Initial schulcloud-mcp server

Read-only MCP server exposing a Schulcloud account to Claude: courses,
column boards, lessons, tasks, and file downloads with text extraction.

The API surface was verified against the live instance rather than
inferred from upstream source, which changed several design decisions:

- The `jwt` cookie works verbatim as `Authorization: Bearer` and lasts 30
  days, so there is no cookie jar and no refresh-session timer.
- Course contents live at /api/v3/course-rooms/{courseId}/board; there is
  no GET /api/v3/courses/{id}.
- Files are a separate service (/api/v3/file/*) with its own OpenAPI doc.
- Board file elements carry no file id; attachments are resolved by
  listing files-storage with parentType=boardnodes and the element id.

Read-only by construction: every client method is a GET, including the
api_get escape hatch. The endpoint is internet-facing by necessity, so a
leaked token being unable to act as the user is the key safety property.

Deploys as a container behind the Pi's existing Caddy, guarded by a
constant-time bearer check. Stateless — no database.

Verified: 28 unit tests, plus a 30-check end-to-end run driving a real
MCP client over Streamable HTTP against the live account.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docker-compose.yml

@@ -0,0 +1,43 @@
+# Standalone Compose file for the Pi.
+#
+# If you already run Caddy and PostgreSQL from another Compose project, either
+# merge the `schulcloud-mcp` service below into that project's file, or keep
+# this file separate and attach it to the existing Caddy network — see the
+# `networks` block at the bottom and deploy/Caddyfile.snippet.
+
+services:
+  schulcloud-mcp:
+    build: .
+    image: schulcloud-mcp:latest
+    container_name: schulcloud-mcp
+    restart: unless-stopped
+    env_file: .env
+    environment:
+      PORT: 8080
+      BIND_HOST: 0.0.0.0
+    # No ports are published to the host: Caddy reaches the container over the
+    # shared Docker network, so the only way in from the internet is through
+    # Caddy's TLS and this server's bearer check.
+    expose:
+      - "8080"
+    networks:
+      - caddy
+    logging:
+      driver: json-file
+      options:
+        max-size: "10m"
+        max-file: "3"
+    security_opt:
+      - no-new-privileges:true
+    read_only: true
+    tmpfs:
+      - /tmp
+    cap_drop:
+      - ALL
+
+networks:
+  caddy:
+    # Set to true once this joins the network your existing Caddy already uses,
+    # and change the name to match (`docker network ls` to find it).
+    external: false
+    name: caddy