feat: Implement session management and search functionality

- Added SDK session, observation, and summary types to types.ts.
- Refactored worker-service to use SessionStore for session management.
- Created SessionSearch class for FTS5 full-text search and structured queries.
- Implemented SessionStore for CRUD operations on SDK sessions, observations, and summaries.
- Added migrations for database schema updates, including new columns and constraints.
- Enhanced search capabilities with filters for projects, types, concepts, and date ranges.

src/hooks/cleanup.ts

@@ -1,4 +1,4 @@
-import { HooksDatabase } from '../services/sqlite/HooksDatabase.js';
+import { SessionStore } from '../services/sqlite/SessionStore.js';
 
 export interface SessionEndInput {
   session_id: string;
@@ -46,7 +46,7 @@ export async function cleanupHook(input?: SessionEndInput): Promise<void> {
     console.error('[claude-mem cleanup] Searching for active SDK session', { session_id, reason });
 
     // Find active SDK session
-    const db = new HooksDatabase();
+    const db = new SessionStore();
     const session = db.findActiveSDKSession(session_id);
 
     if (!session) {