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Excluded from rename: .claude/, devlog/, manascore/ (historical content),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

.prettierignore

@@ -35,10 +35,10 @@ TESTING_STRATEGY_AUTH_CREDITS.md
 .prettiercache
 
 # Astro files with JSX-style comments (valid Astro but Prettier can't parse)
-apps/manacore/apps/landing/src/components/content/HeroSection.astro
-apps/manacore/apps/landing/src/components/sections/ManaPrinciple.astro
-apps/manacore/apps/landing/src/pages/apps/index.astro
-apps/manacore/apps/landing/src/pages/privacy/index.astro
+apps/mana/apps/landing/src/components/content/HeroSection.astro
+apps/mana/apps/landing/src/components/sections/ManaPrinciple.astro
+apps/mana/apps/landing/src/pages/apps/index.astro
+apps/mana/apps/landing/src/pages/privacy/index.astro
 games/mana-games/apps/web/src/layouts/Layout.astro
 games/mana-games/apps/web/src/pages/games/[slug].astro
 games/mana-games/apps/web/src/pages/games/*.astro