fix: address PR #589 review feedback (round 2)

Consolidate three independent RefreshTokenStorage lazy singletons into a
single lock-protected get_shared_storage() function, eliminating race
conditions on concurrent first-access. Remove blanket try/except in
_get_stored_scopes so storage errors propagate as proper MCP errors
instead of silently triggering "please provision" messages. Handle
declined/cancelled elicitation results in Login Flow tools by cleaning up
sessions and returning clear status. Add update_app_password_scopes() to
avoid unnecessary decrypt/re-encrypt when only scopes change. Add
unprovisioned-user early exit and no-op detection to nc_auth_update_scopes.
Remove four dead config fields and misleading NEXTCLOUD_PASSWORD deprecation
warning. Add periodic login flow session cleanup task. Generate separate
Fernet keys per service. Add board cleanup in deck integration test. Gate
CI unit tests on linting and skip Astrolabe build for single-user profile.
Fix test markers from oauth to multi_user_basic for astrolabe integration
tests. Update login_flow.py docstrings to document outbound HTTP calls.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

nextcloud_mcp_server/auth/scope_authorization.py

@@ -9,7 +9,7 @@ from mcp.server.auth.provider import AccessToken
 from mcp.server.fastmcp import Context
 from mcp.server.fastmcp.utilities.context_injection import find_context_parameter
 
-from nextcloud_mcp_server.auth.storage import RefreshTokenStorage
+from nextcloud_mcp_server.auth.storage import get_shared_storage
 from nextcloud_mcp_server.config import get_settings
 
 logger = logging.getLogger(__name__)
@@ -478,18 +478,6 @@ def discover_all_scopes(mcp) -> list[str]:
 # ── Login Flow v2 helpers ────────────────────────────────────────────────
 
 
-_scope_storage_instance = None
-
-
-async def _get_scope_storage():
-    """Get initialized storage instance for scope checks (lazy singleton)."""
-    global _scope_storage_instance
-    if _scope_storage_instance is None:
-        _scope_storage_instance = RefreshTokenStorage.from_env()
-        await _scope_storage_instance.initialize()
-    return _scope_storage_instance
-
-
 async def _get_stored_scopes(user_id: str) -> list[str] | str | None:
     """Look up stored app password scopes for a user.
 
@@ -497,16 +485,16 @@ async def _get_stored_scopes(user_id: str) -> list[str] | str | None:
         - list[str]: Specific scopes granted
         - "all": NULL scopes in DB (legacy = all allowed)
         - None: No stored app password (provisioning required)
-    """
-    try:
-        storage = await _get_scope_storage()
 
-        data = await storage.get_app_password_with_scopes(user_id)
-        if data is None:
-            return None
-        if data["scopes"] is None:
-            return "all"
-        return data["scopes"]
-    except Exception as e:
-        logger.error(f"Failed to check stored scopes for {user_id}: {e}")
+    Raises:
+        Storage/infrastructure exceptions propagate to the caller
+        (require_scopes decorator) for proper MCP error responses.
+    """
+    storage = await get_shared_storage()
+
+    data = await storage.get_app_password_with_scopes(user_id)
+    if data is None:
         return None
+    if data["scopes"] is None:
+        return "all"
+    return data["scopes"]