diff --git a/backend/app/main.py b/backend/app/main.py
index ec4c471..a063c68 100644
--- a/backend/app/main.py
+++ b/backend/app/main.py
@@ -14,6 +14,9 @@ from datetime import datetime, timezone
 from pathlib import Path
 
 from fastapi import FastAPI
+from starlette.middleware.base import BaseHTTPMiddleware
+from starlette.requests import Request as StarletteRequest
+from starlette.responses import Response
 
 from app.core.config import AppConfig
 from app.core.database import close_db, init_db
@@ -109,9 +112,6 @@ app.add_middleware(SessionMiddleware)
 
 
 # --- Security headers middleware (R020: zero outbound telemetry) ---
-from starlette.middleware.base import BaseHTTPMiddleware
-from starlette.requests import Request as StarletteRequest
-from starlette.responses import Response
 
 
 class SecurityHeadersMiddleware(BaseHTTPMiddleware):
@@ -150,7 +150,6 @@ app.include_router(themes_router, prefix="/api")
 # --- Static file serving (production: built frontend) ---
 _static_dir = Path(__file__).resolve().parent.parent / "static"
 if _static_dir.is_dir():
-    from fastapi.staticfiles import StaticFiles
     from fastapi.responses import FileResponse
 
     @app.get("/{full_path:path}")
diff --git a/backend/app/middleware/session.py b/backend/app/middleware/session.py
index cfac82d..1b9e614 100644
--- a/backend/app/middleware/session.py
+++ b/backend/app/middleware/session.py
@@ -43,7 +43,6 @@ class SessionMiddleware(BaseHTTPMiddleware):
 
         # --- Resolve or create session ---
         cookie_value = request.cookies.get("mrip_session")
-        new_session = False
 
         if cookie_value and _is_valid_uuid4(cookie_value):
             session_id = cookie_value
@@ -54,13 +53,11 @@ class SessionMiddleware(BaseHTTPMiddleware):
             else:
                 # Valid UUID but not in DB (expired/purged) — recreate
                 await create_session(db, session_id)
-                new_session = True
                 logger.info("Session recreated (cookie valid, DB miss): %s", session_id)
         else:
             # Missing or invalid cookie — brand new session
             session_id = str(uuid.uuid4())
             await create_session(db, session_id)
-            new_session = True
             logger.info("New session created: %s", session_id)
 
         request.state.session_id = session_id
diff --git a/backend/app/routers/cookies.py b/backend/app/routers/cookies.py
index b28c0db..f6f16b3 100644
--- a/backend/app/routers/cookies.py
+++ b/backend/app/routers/cookies.py
@@ -5,7 +5,7 @@ from __future__ import annotations
 import logging
 from pathlib import Path
 
-from fastapi import APIRouter, Depends, HTTPException, Request, UploadFile
+from fastapi import APIRouter, Depends, Request, UploadFile
 
 from app.dependencies import get_session_id
 
diff --git a/backend/app/routers/downloads.py b/backend/app/routers/downloads.py
index 87d708e..a423f1b 100644
--- a/backend/app/routers/downloads.py
+++ b/backend/app/routers/downloads.py
@@ -54,7 +54,6 @@ async def cancel_download(
     """Delete a download job and remove its file."""
     logger.debug("DELETE /downloads/%s", job_id)
     db = request.app.state.db
-    download_service = request.app.state.download_service
 
     # Fetch the job first to get its session_id and filename
     job = await get_job(db, job_id)
diff --git a/backend/app/services/download.py b/backend/app/services/download.py
index 649af22..0d3bfe6 100644
--- a/backend/app/services/download.py
+++ b/backend/app/services/download.py
@@ -21,7 +21,6 @@ import yt_dlp
 from app.core.config import AppConfig
 from app.core.database import (
     create_job,
-    get_job,
     update_job_progress,
     update_job_status,
 )
diff --git a/backend/tests/conftest.py b/backend/tests/conftest.py
index f87b689..831713a 100644
--- a/backend/tests/conftest.py
+++ b/backend/tests/conftest.py
@@ -3,8 +3,6 @@
 from __future__ import annotations
 
 import asyncio
-import os
-import tempfile
 from datetime import datetime, timezone
 from pathlib import Path
 
diff --git a/backend/tests/test_admin.py b/backend/tests/test_admin.py
index e8a6d29..f4191dd 100644
--- a/backend/tests/test_admin.py
+++ b/backend/tests/test_admin.py
@@ -2,7 +2,6 @@
 
 from __future__ import annotations
 
-import asyncio
 import base64
 from datetime import datetime, timezone
 
@@ -13,9 +12,8 @@ from fastapi import FastAPI
 from httpx import ASGITransport, AsyncClient
 
 from app.core.config import AppConfig
-from app.core.database import close_db, init_db, create_session, create_job
+from app.core.database import close_db, init_db
 from app.middleware.session import SessionMiddleware
-from app.models.job import Job
 from app.routers.admin import router as admin_router
 
 
diff --git a/backend/tests/test_api.py b/backend/tests/test_api.py
index fce65e9..940708a 100644
--- a/backend/tests/test_api.py
+++ b/backend/tests/test_api.py
@@ -9,7 +9,6 @@ from __future__ import annotations
 import asyncio
 
 import pytest
-import pytest_asyncio
 from httpx import ASGITransport, AsyncClient
 
 
diff --git a/backend/tests/test_config.py b/backend/tests/test_config.py
index b225f7d..3aeb55a 100644
--- a/backend/tests/test_config.py
+++ b/backend/tests/test_config.py
@@ -2,11 +2,8 @@
 
 from __future__ import annotations
 
-import os
-import tempfile
 from pathlib import Path
 
-import pytest
 
 from app.core.config import AppConfig
 
diff --git a/backend/tests/test_database.py b/backend/tests/test_database.py
index 0ff8d90..bcf6516 100644
--- a/backend/tests/test_database.py
+++ b/backend/tests/test_database.py
@@ -6,7 +6,6 @@ import asyncio
 import uuid
 from datetime import datetime, timezone
 
-import pytest
 
 from app.core.database import (
     close_db,
diff --git a/backend/tests/test_download_service.py b/backend/tests/test_download_service.py
index 878b2f8..1c83a78 100644
--- a/backend/tests/test_download_service.py
+++ b/backend/tests/test_download_service.py
@@ -7,7 +7,6 @@ and unit tests that only touch the database.
 from __future__ import annotations
 
 import asyncio
-import os
 
 import pytest
 import pytest_asyncio
@@ -104,7 +103,7 @@ async def test_real_download_produces_file_and_events(download_env):
 
     # At least one event should have non-zero percent
     downloading_events = [e for e in events if e.status == "downloading"]
-    has_progress = any(e.percent > 0 for e in downloading_events)
+    any(e.percent > 0 for e in downloading_events)
     # Some very short videos may not report intermediate progress —
     # we still assert downloading events exist
     assert len(downloading_events) > 0
diff --git a/backend/tests/test_file_serving.py b/backend/tests/test_file_serving.py
index 9770c3f..0797d39 100644
--- a/backend/tests/test_file_serving.py
+++ b/backend/tests/test_file_serving.py
@@ -2,9 +2,7 @@
 
 from __future__ import annotations
 
-import uuid
 from datetime import datetime, timezone
-from pathlib import Path
 
 import pytest
 import pytest_asyncio
@@ -12,9 +10,8 @@ from fastapi import FastAPI
 from httpx import ASGITransport, AsyncClient
 
 from app.core.config import AppConfig
-from app.core.database import close_db, init_db, create_job
+from app.core.database import close_db, init_db
 from app.middleware.session import SessionMiddleware
-from app.models.job import Job
 from app.routers.cookies import router as cookies_router
 from app.routers.files import router as files_router
 
diff --git a/backend/tests/test_health.py b/backend/tests/test_health.py
index f55b4df..c61dc65 100644
--- a/backend/tests/test_health.py
+++ b/backend/tests/test_health.py
@@ -9,12 +9,10 @@ Covers:
 
 from __future__ import annotations
 
-import json
 import uuid
 from datetime import datetime, timezone
 
 import pytest
-import pytest_asyncio
 
 from app.core.database import (
     create_job,
@@ -22,7 +20,7 @@ from app.core.database import (
     get_jobs_by_mode,
     get_queue_depth,
 )
-from app.models.job import Job, JobStatus
+from app.models.job import Job
 
 
 # ---------------------------------------------------------------------------
@@ -129,7 +127,6 @@ class TestPublicConfig:
     @pytest.mark.anyio
     async def test_public_config_reflects_actual_config(self, tmp_path):
         """Config values in the response match what AppConfig was built with."""
-        import asyncio
         from datetime import datetime, timezone
 
         from fastapi import FastAPI
@@ -137,7 +134,6 @@ class TestPublicConfig:
 
         from app.core.config import AppConfig
         from app.core.database import close_db, init_db
-        from app.core.sse_broker import SSEBroker
         from app.middleware.session import SessionMiddleware
         from app.routers.system import router as system_router
 
diff --git a/backend/tests/test_models.py b/backend/tests/test_models.py
index 357c6ba..7b70487 100644
--- a/backend/tests/test_models.py
+++ b/backend/tests/test_models.py
@@ -2,7 +2,6 @@
 
 from __future__ import annotations
 
-import pytest
 
 from app.models.job import (
     FormatInfo,
diff --git a/backend/tests/test_purge.py b/backend/tests/test_purge.py
index 78e4738..5690ebf 100644
--- a/backend/tests/test_purge.py
+++ b/backend/tests/test_purge.py
@@ -4,13 +4,11 @@ from __future__ import annotations
 
 import uuid
 from datetime import datetime, timezone, timedelta
-from pathlib import Path
 
 import pytest
-import pytest_asyncio
 
 from app.core.config import AppConfig
-from app.core.database import create_job, init_db, close_db
+from app.core.database import create_job
 from app.models.job import Job
 from app.services.purge import run_purge
 
diff --git a/backend/tests/test_session_middleware.py b/backend/tests/test_session_middleware.py
index d7a546d..6cfc526 100644
--- a/backend/tests/test_session_middleware.py
+++ b/backend/tests/test_session_middleware.py
@@ -2,7 +2,6 @@
 
 from __future__ import annotations
 
-import asyncio
 import uuid
 
 import pytest
diff --git a/backend/tests/test_sse.py b/backend/tests/test_sse.py
index c9d304d..dec757f 100644
--- a/backend/tests/test_sse.py
+++ b/backend/tests/test_sse.py
@@ -11,14 +11,12 @@ import contextlib
 import json
 import uuid
 from datetime import datetime, timezone
-from unittest.mock import AsyncMock, patch
+from unittest.mock import patch
 
-import pytest
 
 from app.core.database import create_job, create_session, get_active_jobs_by_session
-from app.core.sse_broker import SSEBroker
-from app.models.job import Job, JobStatus, ProgressEvent
-from app.routers.sse import KEEPALIVE_TIMEOUT, event_generator
+from app.models.job import Job, ProgressEvent
+from app.routers.sse import event_generator
 
 
 # ---------------------------------------------------------------------------
diff --git a/backend/tests/test_sse_broker.py b/backend/tests/test_sse_broker.py
index 7b638d4..3b8592d 100644
--- a/backend/tests/test_sse_broker.py
+++ b/backend/tests/test_sse_broker.py
@@ -5,7 +5,6 @@ from __future__ import annotations
 import asyncio
 import threading
 
-import pytest
 
 from app.core.sse_broker import SSEBroker