Add comprehensive test suite for backend (133 tests)

Test coverage:
- test_utils.py: formatting helpers (human_size, ticks_to_minutes,
  format_duration, format_bitrate, ffprobe summaries, stream parsing)
- test_path_utils.py: path resolution (prefix, media root mapping,
  edge cases with spaces/special chars)
- test_domain_media.py: Jellyfin item normalization (HDR detection,
  media sources, stream extraction, display formatting)
- test_jobs.py: job template rendering and shell quoting safety
- test_media_index.py: SQLite index CRUD, querying, filtering,
  sorting, pagination
- test_config.py: pydantic-settings env loading
- test_api.py: full FastAPI integration tests with mocked SSH/Jellyfin
  (all endpoints: dashboard, monitoring, media, files, jobs)

All tests run without network/SSH dependencies using mocks.

backend/src/media_library_viewer_api/main.py

@@ -4,6 +4,7 @@ from __future__ import annotations
 
 from contextlib import asynccontextmanager
 
+import uvicorn
 from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 
@@ -49,3 +50,7 @@ app.include_router(jobs.router)
 def health_check() -> dict[str, str]:
     """Simple health check endpoint."""
     return {"status": "ok"}
+
+
+if __name__ == "__main__":
+    uvicorn.run(app, host="0.0.0.0", port=8000)