chore: rename repo mana-monorepo → managarten

Phase-3-Rename des ehemaligen Multi-App-Monorepos zum eigenständigen
Produkt-Repo. Verein heißt mana e.V., Plattform-Domain bleibt mana.how,
apps/mana/ bleibt unverändert — nur der Repo-Container kriegt den
neuen Namen "managarten" (Garten der mana-Apps).

Geändert:
- package.json#name + #description
- README.md (Titel + erster Absatz)
- TROUBLESHOOTING.md
- alle Mac-Mini-Skripte (Pfade ~/projects/mana-monorepo → ~/projects/managarten)
- COMPOSE_PROJECT_NAME-default in scripts/mac-mini/status.sh
- .github/workflows/cd-macmini.yml + mirror-to-forgejo.yml
- apps/docs (astro.config.mjs + content)
- .claude/settings.local.json (Bash-Permission-Pfade)
- alle docs/*.md Pfad-Referenzen
- launchd plists, .env.macmini.example, infrastructure/

Forgejo-Repo + GitHub-Repo bereits via API umbenannt. Lokales
Verzeichnis-Rename + Mac-Mini-Cutover folgen separat.

.env.macmini.example

@@ -21,7 +21,7 @@
 # Compose project name (pinned, do not change)
 # ============================================
 # All Mac Mini containers were originally created under this project
-# name, which mismatches the current directory name (mana-monorepo).
+# name, which mismatches the current directory name (managarten).
 # Pinning the project name here means anyone running 'docker compose ...'
 # from the repo root automatically lands in the same project as the
 # already-running containers, instead of silently spawning a duplicate