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/api/__init__.py

@@ -30,6 +30,8 @@ from app.api.queue import router as queue_router
 from app.api.saved_searches import router as saved_searches_router
 from app.api.search import router as search_router
 from app.api.settings import router as settings_router
+from app.api.shared_links import public_router as shared_links_public_router
+from app.api.shared_links import router as shared_links_router
 from app.api.similarity import router as similarity_router
 from app.api.subscriptions import router as subscriptions_router
 from app.api.url_upload import router as url_upload_router
@@ -64,6 +66,8 @@ router.include_router(search_router)
 router.include_router(queue_router)
 router.include_router(saved_searches_router)
 router.include_router(similarity_router)
+router.include_router(shared_links_router)
+router.include_router(shared_links_public_router)
 router.include_router(duplicates_router)
 router.include_router(webhooks_router)
 router.include_router(database_router)