rename(547): the server is grimoire — package, image, DB defaults, backups

Step 2 of the Scribe -> Grimoire rename.

- src/scribe -> src/grimoire, and every import, patch target, module path,
  hypercorn entry point and `python -m grimoire.restore` with it; pyproject,
  uv.lock and the frontend package are named grimoire.
- Image git.fabledsword.com/bvandeusen/fabledgrimoire; CI's Postgres service
  runs as grimoire / grimoire_test.
- Compose files default the DB user, database and (prod) volume to grimoire,
  each overridable from .env, so an install created as Scribe keeps its data
  by setting POSTGRES_USER, POSTGRES_DB and PGDATA_VOLUME.
- Backups are written as grimoire-<ts>.tar with format grimoire-backup-tar.
  Archives named scribe-* with the scribe-backup-tar manifest still restore
  and are still counted at the destination (folder and S3), with tests.
- Exports, the MCP auth realm, the ASGI scope key and the persistent logger
  carry the new name.

Kept on purpose: the secret-sealing key label stays "scribe.secrets.v1",
because every stored secret was derived under it.

Plugin identity (plugin name, hooks, env vars, .scribe marker, skills) is
step 3.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/api-reference.md

@@ -294,7 +294,7 @@ These serve the plugin's hooks.
 ## Grimoire MCP
 
 Claude clients connect to the built-in MCP server at `POST /mcp` (streamable HTTP,
-Bearer auth with an `fmcp_` key), served by `src/scribe/mcp/`. It is not a REST
+Bearer auth with an `fmcp_` key), served by `src/grimoire/mcp/`. It is not a REST
 surface — it exposes the same data as typed tools (`create_note`, `create_task`,
 `start_planning`, `search`, `enter_project`, …) with
 server-level usage guidance delivered in the MCP `instructions` block. See