feat(11-01): schema, service, and tests for sort_order + reorderCandidates

- Add sortOrder REAL column to threadCandidates schema (default 0)
- Add sort_order column to test helper CREATE TABLE
- Add reorderCandidatesSchema to shared/schemas.ts
- Add ReorderCandidates type to shared/types.ts
- getThreadWithCandidates now orders candidates by sort_order ASC
- createCandidate appends at max sort_order + 1000 (first = 1000)
- Add reorderCandidates service function (transaction, active-only guard)
- Add 5 new tests: ordering, appending, reorder success, resolved guard, missing thread

drizzle/meta/_journal.json

@@ -36,6 +36,13 @@
       "when": 1773693113029,
       "tag": "0004_soft_synch",
       "breakpoints": true
+    },
+    {
+      "idx": 5,
+      "version": "6",
+      "when": 1773696058992,
+      "tag": "0005_clear_micromax",
+      "breakpoints": true
     }
   ]
 }