Phase 3: Graph view, backlinks, quick switcher, export

- Add outgoing_links (JSON) and backlinks_count to Document model
- POST /documents/{id}/detect-links — detect [[uuid]] patterns in content
- GET /documents/{id}/backlinks — documents referencing this doc
- GET /documents/{id}/outgoing-links — documents this doc references
- GET /documents/{id}/links — combined incoming + outgoing
- GET /projects/{id}/graph — full project relationship graph
- GET /search/quick — fuzzy search (Quick Switcher Cmd+K)
- GET /projects/{id}/documents/search — project-scoped search
- GET /documents/{id}/export — markdown|json export
- GET /projects/{id}/export — json|zip export
- 27 new tests

app/database.py

@@ -190,7 +190,9 @@ def _create_schema(sync_conn):
             confidence TEXT,
             reasoning_steps TEXT,
             model_source TEXT,
-            tiptap_content TEXT
+            tiptap_content TEXT,
+            outgoing_links TEXT DEFAULT '[]',
+            backlinks_count INTEGER NOT NULL DEFAULT 0
         )
     """))