feat: implement MCP v2 improvements - simple MVP fixes

Based on Claude Desktop evaluation feedback, implemented minimal fixes:

## Day 1 - Deploy & Debug
- Added /version and /test-tools endpoints for deployment verification
- Added debug logging to list_nodes and list_ai_tools
- Fixed version display in health and initialization responses

## Day 2 - Core Fixes
- Fixed multi-word search to handle phrases like "send slack message"
- Added property deduplication to eliminate duplicate webhook/email properties
- Fixed package name mismatch to handle both formats (@n8n/ prefix variations)

## Day 3 - Polish & Test
- Added simple in-memory cache with 1-hour TTL for essentials
- Added documentation fallback when nodes lack documentation
- All features tested and verified working

Total code changes: ~62 lines as planned
No overengineering, just simple focused fixes

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

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

src/utils/simple-cache.ts

@@ -0,0 +1,37 @@
+/**
+ * Simple in-memory cache with TTL support
+ * No external dependencies needed
+ */
+export class SimpleCache {
+  private cache = new Map<string, { data: any; expires: number }>();
+  
+  constructor() {
+    // Clean up expired entries every minute
+    setInterval(() => {
+      const now = Date.now();
+      for (const [key, item] of this.cache.entries()) {
+        if (item.expires < now) this.cache.delete(key);
+      }
+    }, 60000);
+  }
+  
+  get(key: string): any {
+    const item = this.cache.get(key);
+    if (!item || item.expires < Date.now()) {
+      this.cache.delete(key);
+      return null;
+    }
+    return item.data;
+  }
+  
+  set(key: string, data: any, ttlSeconds: number = 300): void {
+    this.cache.set(key, {
+      data,
+      expires: Date.now() + (ttlSeconds * 1000)
+    });
+  }
+  
+  clear(): void {
+    this.cache.clear();
+  }
+}