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Excluded from rename: .claude/, devlog/, manascore/ (historical content),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>

apps/news/CLAUDE.md

@@ -31,7 +31,7 @@ apps/news/
 | **Web** | SvelteKit 2, Svelte 5 (runes), Tailwind CSS 4 |
 | **Server** | Hono + Bun, Mozilla Readability, JSDOM |
 | **Data** | Local-first (Dexie.js + mana-sync) |
-| **Auth** | mana-core-auth (Better Auth + EdDSA JWT) |
+| **Auth** | mana-auth (Better Auth + EdDSA JWT) |
 
 ## Commands