feat: add stdio transport support for local MCP usage

Add a lightweight stdio transport path so users can run the server
locally with MCP clients like Claude Code using `uvx nextcloud-mcp-server run`.

- New `nextcloud_mcp_server/stdio.py` with minimal FastMCP setup for
  single-user BasicAuth (no OAuth, semantic search, or background sync)
- Default transport changed from streamable-http to stdio
- Dockerfile updated to explicitly use streamable-http for containers
- CLI `--enable-app` now includes news, collectives, and sharing
- README Quick Start section with uvx and MCP client config examples

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

nextcloud_mcp_server/stdio.py

@@ -0,0 +1,128 @@
+"""Lightweight stdio transport for the Nextcloud MCP server.
+
+Provides a minimal FastMCP instance suitable for ``mcp.run(transport="stdio")``.
+Only single-user BasicAuth mode is supported.  Background sync, semantic search,
+OAuth, and observability infrastructure are deliberately excluded.
+"""
+
+from __future__ import annotations
+
+import logging
+from collections.abc import AsyncIterator
+from contextlib import asynccontextmanager
+from dataclasses import dataclass
+from typing import Callable
+
+from mcp.server.fastmcp import Context, FastMCP
+
+from nextcloud_mcp_server.client import NextcloudClient
+from nextcloud_mcp_server.config import get_settings
+from nextcloud_mcp_server.config_validators import AuthMode, validate_configuration
+from nextcloud_mcp_server.context import get_client as get_nextcloud_client
+from nextcloud_mcp_server.server import (
+    configure_calendar_tools,
+    configure_collectives_tools,
+    configure_contacts_tools,
+    configure_cookbook_tools,
+    configure_deck_tools,
+    configure_news_tools,
+    configure_notes_tools,
+    configure_sharing_tools,
+    configure_tables_tools,
+    configure_webdav_tools,
+)
+
+logger = logging.getLogger(__name__)
+
+
+@dataclass
+class StdioContext:
+    """Minimal lifespan context for stdio transport.
+
+    Carries only the shared :class:`NextcloudClient`.  The ``client``
+    attribute satisfies the duck-type check in
+    :func:`nextcloud_mcp_server.context.get_client`.
+    """
+
+    client: NextcloudClient
+
+
+@asynccontextmanager
+async def stdio_lifespan(server: FastMCP) -> AsyncIterator[StdioContext]:
+    """Create and tear down a single :class:`NextcloudClient`."""
+    logger.info("Starting MCP server in stdio mode (single-user BasicAuth)")
+    client = NextcloudClient.from_env()
+    try:
+        yield StdioContext(client=client)
+    finally:
+        await client.close()
+        logger.info("stdio session shut down")
+
+
+def get_stdio_mcp(enabled_apps: list[str] | None = None) -> FastMCP:
+    """Return a :class:`FastMCP` instance configured for stdio transport.
+
+    Parameters
+    ----------
+    enabled_apps:
+        Whitelist of Nextcloud app names to register.  ``None`` means all.
+
+    Raises
+    ------
+    ValueError
+        If the current configuration is not single-user BasicAuth.
+    """
+    settings = get_settings()
+    mode, config_errors = validate_configuration(settings)
+
+    if config_errors:
+        raise ValueError(
+            f"Configuration validation failed for {mode.value} mode:\n"
+            + "\n".join(f"  - {err}" for err in config_errors)
+        )
+
+    if mode != AuthMode.SINGLE_USER_BASIC:
+        raise ValueError(
+            f"stdio transport only supports single-user BasicAuth mode, "
+            f"but detected {mode.value}. Set NEXTCLOUD_HOST, NEXTCLOUD_USERNAME, "
+            f"and NEXTCLOUD_PASSWORD."
+        )
+
+    mcp = FastMCP("Nextcloud MCP", lifespan=stdio_lifespan)
+
+    # --- capabilities resource (mirrors app.py) ---
+    @mcp.resource("nc://capabilities")
+    async def nc_get_capabilities():
+        """Get the Nextcloud Host capabilities"""
+        ctx: Context = mcp.get_context()
+        client = await get_nextcloud_client(ctx)
+        return await client.capabilities()
+
+    # --- tool registration ---
+    available_apps: dict[str, Callable] = {
+        "notes": configure_notes_tools,
+        "tables": configure_tables_tools,
+        "webdav": configure_webdav_tools,
+        "sharing": configure_sharing_tools,
+        "calendar": configure_calendar_tools,
+        "collectives": configure_collectives_tools,
+        "contacts": configure_contacts_tools,
+        "cookbook": configure_cookbook_tools,
+        "deck": configure_deck_tools,
+        "news": configure_news_tools,
+    }
+
+    if enabled_apps is None:
+        enabled_apps = list(available_apps.keys())
+
+    for app_name in enabled_apps:
+        if app_name in available_apps:
+            logger.info(f"Configuring {app_name} tools")
+            available_apps[app_name](mcp)
+        else:
+            logger.warning(
+                f"Unknown app: {app_name}. "
+                f"Available apps: {list(available_apps.keys())}"
+            )
+
+    return mcp