fix(core): bump SCHEMA_VERSION to 49 so the nodeId task-column migration runs

Migration 49 (`ALTER TABLE tasks ADD COLUMN nodeId TEXT`) was added with
SCHEMA_VERSION still pinned to 48. Existing DBs at version 48 hit the
`if (version >= SCHEMA_VERSION) return;` early exit, so the column was never
created — `TaskStore.listTasks` then crashed at startup with
`no such column: nodeId` and the dashboard exited before initialization.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/core/src/db.ts

@@ -86,7 +86,7 @@ export function probeFts5(db: DatabaseSync): boolean {
 
 // ── Schema Definition ────────────────────────────────────────────────
 
-const SCHEMA_VERSION = 48;
+const SCHEMA_VERSION = 49;
 
 function normalizeTaskComments(
   steeringComments: SteeringComment[] | undefined,