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)

app/views/share.py

@@ -0,0 +1,28 @@
+"""Public view for accessing a shared document link.
+
+This route does NOT require authentication — it is the landing page
+that link recipients visit.  The page fetches link metadata via the
+public ``/api/share/{token}/info`` JSON endpoint and then renders the
+appropriate download UI (password gate or direct download button).
+"""
+
+import logging
+import pathlib
+
+from fastapi import APIRouter, Request
+from fastapi.templating import Jinja2Templates
+
+logger = logging.getLogger(__name__)
+router = APIRouter()
+
+_templates_dir = pathlib.Path(__file__).parents[2] / "frontend" / "templates"
+templates = Jinja2Templates(directory=str(_templates_dir))
+
+
+@router.get("/share/{token}")
+async def shared_link_view(request: Request, token: str):
+    """Render the public share landing page for a given token."""
+    return templates.TemplateResponse(
+        "shared_link_view.html",
+        {"request": request, "token": token},
+    )

app/views/shared_links.py

@@ -0,0 +1,24 @@
+"""View route for the Shared Links management page.
+
+Renders the ``shared_links.html`` template where authenticated users can
+create, view, and revoke their document share links.
+"""
+
+import logging
+
+from fastapi import APIRouter, Request
+
+from app.views.base import require_login, templates
+
+logger = logging.getLogger(__name__)
+router = APIRouter()
+
+
+@router.get("/shared-links")
+@require_login
+async def shared_links_page(request: Request):
+    """Render the Shared Links management page."""
+    return templates.TemplateResponse(
+        "shared_links.html",
+        {"request": request, "page_title": "Shared Links"},
+    )