feat(mcp): ready for a remote server: quiet logs and allowed domains

- Logs default to warnings and errors (MCP_LOG_LEVEL): the library logged
  every tool on every request (~48 lines per call).
- DNS rebinding protection on /mcp, as the MCP spec asks of HTTP servers:
  the Host header must be in MCP_ALLOWED_HOSTS (default: localhost; compose
  default mcp.taskstream.pireon.dev,localhost) and a browser Origin, when
  present, too; otherwise 403 with a JSON-RPC error. Uses the official
  validators from @modelcontextprotocol/server.
- Test for allowed/foreign Host and Origin; .env.example, compose and
  docs/09-mcp.md document the variables; Word/PDF regenerated.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/mcp/src/app/mcp.spec.ts

@@ -1,6 +1,11 @@
 import { INestApplication } from '@nestjs/common';
 import { Test } from '@nestjs/testing';
-import { createServer, IncomingMessage, Server } from 'node:http';
+import {
+  createServer,
+  IncomingMessage,
+  request as httpRequest,
+  Server,
+} from 'node:http';
 import { AddressInfo } from 'node:net';
 import { TASKSTREAM_API_URL } from './api/taskstream-api';
 import { AppModule } from './app.module';
@@ -211,4 +216,50 @@ describe('TaskStream MCP', () => {
     expect(result.isError).toBe(true);
     expect(received).toHaveLength(0);
   });
+
+  /** A raw POST /mcp with chosen Host / Origin headers (fetch would not let us set Host). */
+  function rawPost(headers: Record<string, string>): Promise<number> {
+    const { port } = new URL(url);
+    return new Promise((resolve, reject) => {
+      const req = httpRequest(
+        {
+          host: '127.0.0.1',
+          port,
+          path: '/mcp',
+          method: 'POST',
+          headers: {
+            'content-type': 'application/json',
+            accept: 'application/json, text/event-stream',
+            'mcp-protocol-version': '2025-06-18',
+            ...headers,
+          },
+        },
+        (res) => {
+          res.resume();
+          resolve(res.statusCode ?? 0);
+        },
+      );
+      req.on('error', reject);
+      req.end(JSON.stringify({ jsonrpc: '2.0', id: 1, method: 'tools/list' }));
+    });
+  }
+
+  it('only answers on its own domain (DNS rebinding protection)', async () => {
+    // Default allowlist: localhost only (MCP_ALLOWED_HOSTS sets the real domain).
+    expect(await rawPost({ host: `localhost:${new URL(url).port}` })).toBe(200);
+    expect(await rawPost({ host: 'evil.example' })).toBe(403);
+    expect(
+      await rawPost({
+        host: `localhost:${new URL(url).port}`,
+        origin: 'https://evil.example',
+      }),
+    ).toBe(403);
+    expect(
+      await rawPost({
+        host: `localhost:${new URL(url).port}`,
+        origin: 'http://localhost:6274',
+      }),
+    ).toBe(200);
+    expect((await fetch(`${url}/health`)).status).toBe(200);
+  });
 });