fix(asgi): redirect /mcp → /mcp/ for clients that omit the trailing slash

Starlette's Mount("/mcp", ...) only matches /mcp/* paths. A POST to bare
/mcp falls through to the catch-all Django mount and returns 404. The
fast-agent MCP client and the README example both used the no-slash URL,
so the validator was never able to initialize a session — every call
landed in django.request.

Adds a 307 redirect at /mcp so any client URL works, and points the
validator config at /mcp/ directly to skip the redirect round-trip.
Also gitignores fastagent.jsonl (a runtime log file fast-agent writes
into the working directory).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

validator/fastagent.config.yaml

@@ -27,6 +27,6 @@ mcp:
     # override the URL in fastagent.secrets.yaml or via Ansible if remote.
     mnemosyne:
       transport: http
-      url: "http://localhost:22091/mcp"
+      url: "http://localhost:22091/mcp/"
       # Bearer token in fastagent.secrets.yaml (provisioned via
       # `python manage.py create_mcp_token <user>`).