feat: eager vLLM warmup and smart page titles in paginate stage

- Add warmup() to LlmProvider interface for eager subprocess startup
- ManagedVllmProvider.warmup() starts vLLM in background on project load
- ProviderRegistry.warmupAll() triggers all managed providers
- NamedProvider proxies warmup() to inner provider
- paginate stage generates LLM-powered descriptive page titles when
  available, cached by content hash, falls back to generic "Page N"
- project-mcp-endpoint calls warmupAll() on router creation so vLLM
  is loading while the session initializes

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

stack/docker-compose.yml

@@ -29,6 +29,8 @@ services:
       MCPD_HOST: "0.0.0.0"
       MCPD_LOG_LEVEL: ${MCPD_LOG_LEVEL:-info}
       MCPD_NODE_RUNNER_IMAGE: mysources.co.uk/michal/mcpctl-node-runner:latest
+      MCPD_PYTHON_RUNNER_IMAGE: mysources.co.uk/michal/mcpctl-python-runner:latest
+      MCPD_RATE_LIMIT_MAX: "500"
       MCPD_MCP_NETWORK: mcp-servers
     depends_on:
       postgres: