chore: complete ManaCore → Mana rename (docs, go modules, plists, images)

Final cleanup of references missed in previous rename commits:

- Dockerfiles: PUBLIC_MANA_CORE_AUTH_URL → PUBLIC_MANA_AUTH_URL
- Go modules: github.com/manacore/* → github.com/mana/* (7 go.mod files)
- launchd plists: com.manacore.* → com.mana.* (14 files renamed + content)
- Image assets: *_Manacore_AI_Credits* → *_Mana_AI_Credits* (11 files)
- .env.example files: ManaCore brand strings → Mana
- .prettierignore: stale apps/manacore/* paths → apps/mana/*
- Markdown docs (CLAUDE.md, /docs/*): mana-core-auth → mana-auth, etc.

Excluded from rename: .claude/, devlog/, manascore/ (historical content),
client testimonials, blueprints, npm package refs (@mana-core/*).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

NewAppIdeas/Roblox Reimagined/Optimaler-Stack.md

@@ -345,7 +345,7 @@ Transaktion: Alice kauft Item in Bobs Game fuer 100 Mana
 │  TypeScript (30%)                                   │
 │  ├── Svelte 5 UI (Editor, Marketplace, Social)      │
 │  ├── Hono Services (auth, credits, user, subs)      │
-│  ├── Shared Packages (@manacore/*)                  │
+│  ├── Shared Packages (@mana/*)                  │
 │  ├── User Game Scripts (→ WASM kompiliert)           │
 │  └── Local-First Layer (Dexie.js)                   │
 │                                                     │