feat: Implement ADR-016 Smithery stateless deployment mode

Adds support for Smithery hosted deployment with stateless operation:

- Add DeploymentMode enum with SELF_HOSTED and SMITHERY_STATELESS modes
- Add get_deployment_mode() to detect mode from SMITHERY_DEPLOYMENT env var
- Update get_client() to create per-request clients from session config
- Add conditional tool registration (skip semantic search in Smithery mode)
- Add conditional /app admin UI mounting (skip in Smithery mode)
- Create smithery.yaml with configSchema for user credentials
- Create Dockerfile.smithery for minimal stateless container
- Create smithery_main.py entrypoint for Smithery deployment

In Smithery mode:
- Users provide nextcloud_url, username, app_password via session config
- Each request creates a fresh NextcloudClient (no state between requests)
- Semantic search tools are disabled (no vector database)
- Admin UI (/app) is disabled (no webhooks, vector viz)

All existing self-hosted functionality remains unchanged.

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

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

nextcloud_mcp_server/smithery_main.py

@@ -0,0 +1,60 @@
+"""Smithery-specific entrypoint for stateless deployment.
+
+ADR-016: This entrypoint is used when deploying on Smithery's hosting platform.
+It configures the server for stateless operation with per-session authentication.
+
+Features disabled in Smithery mode:
+- Vector sync / semantic search (no persistent storage)
+- Admin UI at /app (no webhooks, no vector viz)
+- OAuth provisioning tools (no token storage)
+
+Features enabled:
+- Core Nextcloud tools (notes, calendar, contacts, files, deck, tables, cookbook)
+- Per-session app password authentication via Smithery configSchema
+- Health check endpoints (/health/live, /health/ready)
+"""
+
+import logging
+import os
+
+import uvicorn
+
+from nextcloud_mcp_server.config import setup_logging
+
+logger = logging.getLogger(__name__)
+
+
+def main():
+    """Start the MCP server in Smithery stateless mode."""
+    # Setup logging first
+    setup_logging()
+
+    # Force stateless mode environment variables
+    os.environ["SMITHERY_DEPLOYMENT"] = "true"
+    os.environ["VECTOR_SYNC_ENABLED"] = "false"
+
+    logger.info("Starting Nextcloud MCP Server in Smithery stateless mode")
+
+    # Import app after setting environment variables
+    from nextcloud_mcp_server.app import get_app
+
+    # Create the app with streamable-http transport (required for Smithery)
+    app = get_app(transport="streamable-http")
+
+    # Smithery sets PORT environment variable
+    port = int(os.environ.get("PORT", 8081))
+
+    logger.info(f"Listening on port {port}")
+
+    uvicorn.run(
+        app,
+        host="0.0.0.0",
+        port=port,
+        log_level="info",
+        # Disable access log for cleaner output
+        access_log=False,
+    )
+
+
+if __name__ == "__main__":
+    main()