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>

docker-compose.quickstart.yml

@@ -1,4 +1,4 @@
-# Fabled Assistant — Quick Start
+# Fabled Scribe — Quick Start
 #
 # No build required. Pulls the latest pre-built image from the registry.
 #
@@ -13,7 +13,7 @@
 
 services:
   app:
-    image: git.fabledsword.com/bvandeusen/fabledassistant:latest
+    image: git.fabledsword.com/bvandeusen/fabledscribe:latest
     ports:
       - "5000:5000"
     environment: