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>

mkdocs.yml

@@ -12,11 +12,34 @@ theme:
     - navigation.instant
     - search.suggest
     - content.code.copy
+    - navigation.sections
+    - navigation.top
+    - toc.integrate
+  palette:
+    - scheme: default
+      primary: blue
+      accent: blue
+      toggle:
+        icon: material/brightness-7
+        name: Switch to dark mode
+    - scheme: slate
+      primary: blue
+      accent: blue
+      toggle:
+        icon: material/brightness-4
+        name: Switch to light mode
 nav:
   - Getting Started:
       - Setup Wizard: SetupWizard
       - User Guide: UserGuide
       - Browser Extension: BrowserExtension
+  - How-To Guides:
+      - Overview: HowToGuides.md
+      - HP Enterprise Printer: howto/HPPrinterSetup.md
+      - Fujitsu ScanSnap: howto/SnapScanSetup.md
+      - Watched Folder: howto/WatchedFolderSetup.md
+      - Email Ingestion: howto/EmailIngestion.md
+      - Mobile Scanning: howto/MobileScanning.md
   - API: API
   - Deployment:
       - Overview: DeploymentGuide