Prepare for a live account: separate the indexes, and probe new routes live

With .env pointing at the real account, testing against the local instance
became dangerous: process env beats --env-file, so a local smoke run would
crawl fixtures straight into the live index, where a per-course refresh
carries them forward indefinitely. mcp-env.sh now pins its own database
(schulcloud_local) and mirror as well as the instance.

The override publishes the server on MCP_HOST_PORT and takes
CRAWL_INTERVAL_MS from .env, since what_changed can only report what
happened between crawls. The build context leaves out tmp/, which holds a
mirror of the account's files, and local-instance/.

probe checks live what the gap fixes established locally: the /api/v1 course
and user routes, classes, room allowedOperations as an object, and the
preview enums on a real file. A failure there means a feature degrades
rather than breaks.

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

.env.example

@@ -26,6 +26,10 @@ MCP_AUTH_TOKEN=
 PORT=8080
 BIND_HOST=0.0.0.0
 
+# Local Docker only: the loopback port docker-compose.override.yml publishes the
+# container on. Default 8080; change it when that port is already taken.
+# MCP_HOST_PORT=8080
+
 # ---------------------------------------------------------------------------
 # Index and file mirror (optional — without these the server runs live-only:
 # search crawls on every call, and the CLI's /api surface is unavailable)