feat(api): MCP server endpoint — expose AI tools to external clients

Mount an MCP (Model Context Protocol) server at /api/v1/mcp in the
unified Hono API. External clients like Claude Desktop, Cursor, and
VS Code Copilot can discover and call all 29 Mana tools via the
standard MCP protocol.

Architecture:
- WebStandardStreamableHTTPServerTransport for Bun/Hono compatibility
- AI_TOOL_CATALOG → MCP tool definitions with JSON Schema (via Zod)
- Stateful sessions with Mcp-Session-Id header
- Auth via existing authMiddleware (JWT or API key)

Phase 1 scope: tools/list returns all 29 tools with schemas,
tools/call acknowledges with descriptive messages. Phase 2 will add
actual DB reads/writes via sync_changes.

Usage:
  Claude Desktop config:
  {"mcpServers": {"mana": {"url": "http://localhost:3060/api/v1/mcp"}}}

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/api/src/index.ts

@@ -15,6 +15,9 @@ import {
 	rateLimitMiddleware,
 } from '@mana/shared-hono';
 
+// MCP server
+import { handleMcpRequest } from './mcp/server';
+
 // Module routes
 import { calendarRoutes } from './modules/calendar/routes';
 import { contactsRoutes } from './modules/contacts/routes';
@@ -48,6 +51,10 @@ app.route('/health', healthRoute('mana-api'));
 app.use('/api/*', rateLimitMiddleware({ max: 200, windowMs: 60_000 }));
 app.use('/api/*', authMiddleware());
 
+// ─── MCP Endpoint ──────────────────────────────────────────
+// Streamable HTTP transport: POST (messages), GET (SSE stream), DELETE (close)
+app.all('/api/v1/mcp', (c) => handleMcpRequest(c.req.raw));
+
 // ─── Module Routes ──────────────────────────────────────────
 app.route('/api/v1/calendar', calendarRoutes);
 app.route('/api/v1/contacts', contactsRoutes);