fix: remove unused nodes-v2.db and update database paths

- Removed unused empty nodes-v2.db file
- Updated NodeDocumentationService to use nodes.db as default
- Updated test file to use correct database
- Added secret scanning exclusion for database files

This prevents confusion about which database is actually used and removes
the file that GitHub's security advisor was flagging.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

src/services/node-documentation-service.ts

@@ -64,7 +64,7 @@ export class NodeDocumentationService {
   private initialized: Promise<void>;
   
   constructor(dbPath?: string) {
-    this.dbPath = dbPath || process.env.NODE_DB_PATH || path.join(process.cwd(), 'data', 'nodes-v2.db');
+    this.dbPath = dbPath || process.env.NODE_DB_PATH || path.join(process.cwd(), 'data', 'nodes.db');
     
     // Ensure directory exists
     const dbDir = path.dirname(this.dbPath);