feat: Implement n8n-MCP Enhancement Plan v2.1 Final

- Implement simple node loader supporting n8n-nodes-base and langchain packages
- Create parser handling declarative, programmatic, and versioned nodes
- Build documentation mapper with 89% coverage (405/457 nodes)
- Setup SQLite database with minimal schema
- Create rebuild script for one-command database updates
- Implement validation script for critical nodes
- Update MCP server with documentation-focused tools
- Add npm scripts for streamlined workflow

Successfully loads 457/458 nodes with accurate documentation mapping.
Versioned node detection working (46 nodes detected).
3/4 critical nodes pass validation tests.

Known limitations:
- Slack operations extraction incomplete for some versioned nodes
- One langchain node fails due to missing dependency
- No AI tools detected (none have usableAsTool flag)

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

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

src/database/schema.sql

@@ -0,0 +1,24 @@
+-- Ultra-simple schema for MVP
+CREATE TABLE IF NOT EXISTS nodes (
+  node_type TEXT PRIMARY KEY,
+  package_name TEXT NOT NULL,
+  display_name TEXT NOT NULL,
+  description TEXT,
+  category TEXT,
+  development_style TEXT CHECK(development_style IN ('declarative', 'programmatic')),
+  is_ai_tool INTEGER DEFAULT 0,
+  is_trigger INTEGER DEFAULT 0,
+  is_webhook INTEGER DEFAULT 0,
+  is_versioned INTEGER DEFAULT 0,
+  version TEXT,
+  documentation TEXT,
+  properties_schema TEXT,
+  operations TEXT,
+  credentials_required TEXT,
+  updated_at DATETIME DEFAULT CURRENT_TIMESTAMP
+);
+
+-- Minimal indexes for performance
+CREATE INDEX IF NOT EXISTS idx_package ON nodes(package_name);
+CREATE INDEX IF NOT EXISTS idx_ai_tool ON nodes(is_ai_tool);
+CREATE INDEX IF NOT EXISTS idx_category ON nodes(category);