refactor: rename Fabled Assistant to Fabled Scribe

Updates user-visible branding across frontend (PWA manifest, page title,
Settings, push fallback), backend (email templates and subjects, LLM
system prompt, CalDAV displayname, SMTP from-name default), README,
quickstart compose, and MCP server description.

Also updates the CI image path and quickstart image reference to
git.fabledsword.com/bvandeusen/fabledscribe in preparation for the
Forgejo repo rename. Internal Python package, env vars, and database
schema unchanged.

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

.forgejo/workflows/ci.yml

@@ -57,7 +57,7 @@ permissions:
 
 env:
   REGISTRY: git.fabledsword.com
-  IMAGE: git.fabledsword.com/bvandeusen/fabledassistant
+  IMAGE: git.fabledsword.com/bvandeusen/fabledscribe
 
 jobs:
   typecheck: