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>

cloudflared-config.yml

@@ -70,10 +70,10 @@ ingress:
   # - hostname: planta.mana.how
   #   service: http://localhost:XXXX
 
-  # ManaDeck App
-  - hostname: manadeck.mana.how
+  # Cards App
+  - hostname: cards.mana.how
     service: http://localhost:5023
-  - hostname: manadeck-api.mana.how
+  - hostname: cards-api.mana.how
     service: http://localhost:3009
 
   # Storage App