feat(sharing): add document sharing with expiring links

- Add SharedLink model with token, expiry, view limit, password hash
- Add migration 025_add_shared_links
- Add API endpoints: create, list, revoke (auth) + public info/download
- Add management UI at /shared-links with revoke controls
- Add public share landing page at /share/{token}
- Add Share button on file_view.html
- Add Shared Links to user dropdown in common.js
- Write 35 unit tests covering all scenarios
- Update UserGuide.md with sharing documentation

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

app/views/__init__.py

@@ -25,6 +25,8 @@ from app.views.plans import router as plans_router  # Admin Plan Designer
 from app.views.queue import router as queue_router
 from app.views.search import router as search_router
 from app.views.settings import router as settings_router
+from app.views.share import router as share_router
+from app.views.shared_links import router as shared_links_router
 from app.views.status import router as status_router
 from app.views.subscriptions import router as subscriptions_router  # Pricing + subscription pages
 from app.views.wizard import router as wizard_router
@@ -35,6 +37,8 @@ router.include_router(wizard_router)  # Wizard first (for /setup)
 router.include_router(db_wizard_router)  # Database wizard
 router.include_router(admin_users_router)  # Admin user management
 router.include_router(api_tokens_router)  # API token management
+router.include_router(shared_links_router)  # Shared links management
+router.include_router(share_router)  # Public share landing pages (no auth)
 router.include_router(backup_router)  # Backup dashboard
 router.include_router(general_router)
 router.include_router(status_router)