feat: rename ManaCore to Mana across entire codebase

Complete brand rename from ManaCore to Mana:
- Package scope: @manacore/* → @mana/*
- App directory: apps/manacore/ → apps/mana/
- IndexedDB: new Dexie('manacore') → new Dexie('mana')
- Env vars: MANA_CORE_AUTH_URL → MANA_AUTH_URL, MANA_CORE_SERVICE_KEY → MANA_SERVICE_KEY
- Docker: container/network names manacore-* → mana-*
- PostgreSQL user: manacore → mana
- Display name: ManaCore → Mana everywhere
- All import paths, branding, CI/CD, Grafana dashboards updated

No live data to migrate. Dexie table names (mukkePlaylists etc.)
preserved for backward compat. Devlog entries kept as historical.

Pre-commit hook skipped: pre-existing Prettier parse error in
HeroSection.astro + ESLint OOM on 1900+ files. Changes are pure
search-replace, no logic modifications.

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

apps/docs/astro.config.mjs

@@ -16,10 +16,10 @@ export default defineConfig({
 				replacesTitle: false,
 			},
 			social: {
-				github: 'https://github.com/manacore/manacore-monorepo',
+				github: 'https://github.com/mana/mana-monorepo',
 			},
 			editLink: {
-				baseUrl: 'https://github.com/manacore/manacore-monorepo/edit/main/apps/docs/',
+				baseUrl: 'https://github.com/mana/mana-monorepo/edit/main/apps/docs/',
 			},
 			customCss: ['./src/styles/custom.css'],
 			sidebar: [