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>

docs/ANALYTICS.md

@@ -1,6 +1,6 @@
 # Analytics & Event Tracking
 
-ManaCore verwendet Umami für Web Analytics. Alle Events werden zu `stats.mana.how` gesendet.
+Mana verwendet Umami für Web Analytics. Alle Events werden zu `stats.mana.how` gesendet.
 
 ## Umami Dashboard
 
@@ -45,7 +45,7 @@ injectUmamiAnalytics(html)    → <script defer src="stats.mana.how/script.js" d
 | App | Env-Variable |
 |-----|-------------|
 | Chat | `UMAMI_WEBSITE_ID_CHAT_LANDING` |
-| ManaCore | `UMAMI_WEBSITE_ID_MANACORE_LANDING` |
+| Mana | `UMAMI_WEBSITE_ID_MANACORE_LANDING` |
 | Cards | `UMAMI_WEBSITE_ID_CARDS_LANDING` |
 | Calendar | `UMAMI_WEBSITE_ID_CALENDAR_LANDING` |
 | Clock | `UMAMI_WEBSITE_ID_CLOCK_LANDING` |
@@ -60,7 +60,7 @@ injectUmamiAnalytics(html)    → <script defer src="stats.mana.how/script.js" d
 | App | Env-Variable |
 |-----|-------------|
 | Chat | `UMAMI_WEBSITE_ID_CHAT` |
-| ManaCore | `UMAMI_WEBSITE_ID_MANACORE` |
+| Mana | `UMAMI_WEBSITE_ID_MANACORE` |
 | Todo | `UMAMI_WEBSITE_ID_TODO` |
 | Calendar | `UMAMI_WEBSITE_ID_CALENDAR` |
 | Clock | `UMAMI_WEBSITE_ID_CLOCK` |