feat(docs): add built-in help section with How-To guides embedded in app

- Add MkDocs Material docs build stage to Dockerfile and Dockerfile.local
- Mount pre-built docs as static files at /help/ in FastAPI (app/main.py)
- Add app/views/help.py with /help → /help/ permanent redirect route
- Register help router in app/views/__init__.py
- Add Help nav link to base.html (public + app nav, desktop + mobile)
- Create how-to guides: HP printer, ScanSnap, watched folder, email ingestion, mobile scanning
- Update mkdocs.yml with How-To Guides section and Material theme palette
- Add optional docs service (squidfunk/mkdocs-material) to docker-compose.yaml with docs profile
- Add mkdocs-material to requirements-dev.txt
- Add /docs_build to .gitignore
- Add tests for help view (8 tests, 100% coverage on help.py)

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

app/main.py

@@ -202,6 +202,15 @@ if os.path.exists(static_dir):
 else:
     print(f"WARNING: Static directory not found at {static_dir}. Static files will not be served.")
 
+# Mount the built MkDocs documentation site at /help/
+# The docs are pre-built into docs_build/ during the Docker image build.
+# When running locally, run `mkdocs build` from the repo root first.
+docs_build_dir = pathlib.Path(__file__).parents[1] / "docs_build"
+if os.path.exists(docs_build_dir):
+    app.mount("/help", StaticFiles(directory=str(docs_build_dir), html=True), name="help_docs")
+else:
+    print(f"INFO: Help docs not found at {docs_build_dir}. Run 'mkdocs build' to generate them.")
+
 
 # Custom exception handlers that return JSON for API routes and HTML for frontend routes
 @app.exception_handler(HTTPException)