fix: memory leak in session removal - close MCP server properly (#471) (#472)

- Add close() method to N8NDocumentationMCPServer that:
  - Calls server.close() (MCP SDK cleanup)
  - Clears internal cache
  - Nullifies service references to help GC
- Update removeSession() to call server.close() before releasing references

Root cause: removeSession() deleted server from map but didn't call cleanup
Evidence: Production server memory grew ~1GB in 43 minutes (10% to 35%)

Conceived by Romuald Członkowski - https://www.aiadvisors.pl/en

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

Co-authored-by: Romuald Członkowski <romualdczlonkowski@MacBook-Pro-Romuald.local>
Co-authored-by: Claude <noreply@anthropic.com>

dist/mcp/server.js

@@ -147,6 +147,19 @@ class N8NDocumentationMCPServer {
         });
         this.setupHandlers();
     }
+    async close() {
+        try {
+            await this.server.close();
+            this.cache.clear();
+            this.db = null;
+            this.repository = null;
+            this.templateService = null;
+            this.earlyLogger = null;
+        }
+        catch (error) {
+            logger_1.logger.warn('Error closing MCP server', { error: error instanceof Error ? error.message : String(error) });
+        }
+    }
     async initializeDatabase(dbPath) {
         try {
             if (this.earlyLogger) {