refactor: rename ManaDeck to Cards across entire monorepo

Rename the flashcard/deck management app from ManaDeck to Cards:
- Directory: apps/manadeck → apps/cards, packages/manadeck-database → packages/cards-database
- Packages: @manadeck/* → @cards/*, @manacore/manadeck-database → @manacore/cards-database
- Domain: manadeck.mana.how → cards.mana.how
- Storage: manadeck-storage → cards-storage
- Database: manadeck → cards
- All shared packages, infra configs, services, i18n, and docs updated
- 244 files changed, zero remaining manadeck references

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

docker/prometheus/prometheus.yml

@@ -267,7 +267,7 @@ scrape_configs:
           - https://planta.mana.how
           - https://calc.mana.how
           - https://zitare.mana.how
-          - https://manadeck.mana.how
+          - https://cards.mana.how
           - https://skilltree.mana.how
           - https://mukke.mana.how
           - https://citycorners.mana.how