feat: implement Story 1.4 — recent view and drag-and-drop organization

Add sortOrder column to diagrams, extend PATCH endpoint with projectId
and sortOrder fields, add POST /diagrams/reorder bulk endpoint with
ownership verification and duplicate ID validation. Enhance RecentList
with lastAiMessage preview subtitle. Implement @dnd-kit drag-and-drop
in ProjectTree sidebar with cross-project moves, intra-project reorder,
optimistic updates, drag overlay, drop indicators, and keyboard/pointer
sensor support. Context-aware GET ordering: sortOrder for project views,
updatedAt for recent/all views. 141 tests pass.

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

packages/db/migrations/meta/_journal.json

@@ -8,6 +8,13 @@
       "when": 1771801819664,
       "tag": "0000_simple_hobgoblin",
       "breakpoints": true
+    },
+    {
+      "idx": 1,
+      "version": "7",
+      "when": 1771885601062,
+      "tag": "0001_fuzzy_gorilla_man",
+      "breakpoints": true
     }
   ]
-}
+}