Add complete ai.card Rust implementation

- Implement complete Rust API server with axum framework
- Add database abstraction supporting PostgreSQL and SQLite
- Implement comprehensive gacha system with probability calculations
- Add JWT authentication with atproto DID integration
- Create card master data system with rarities (Normal, Rare, SuperRare, Kira, Unique)
- Implement draw history tracking and collection management
- Add API endpoints for authentication, card drawing, and collection viewing
- Include database migrations for both PostgreSQL and SQLite
- Maintain full compatibility with Python API implementation
- Add comprehensive documentation and development guide

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

python/api/.env.example

@@ -0,0 +1,32 @@
+# Application
+APP_NAME=ai.card
+APP_VERSION=0.1.0
+DEBUG=false
+
+# Database (Local PostgreSQL)
+DATABASE_URL=postgresql+asyncpg://postgres:postgres@localhost:5432/aicard
+
+# Database (Supabase - optional)
+DATABASE_URL_SUPABASE=postgresql+asyncpg://postgres.xxxxxxxxxxxx:password@aws-0-region.pooler.supabase.com:5432/postgres
+USE_SUPABASE=false
+
+# atproto (optional)
+ATPROTO_PDS_URL=https://bsky.social
+ATPROTO_HANDLE=your.handle
+ATPROTO_PASSWORD=your-app-password
+
+# Card probabilities (in percentage)
+PROB_NORMAL=99.789
+PROB_RARE=0.1
+PROB_SUPER_RARE=0.01
+PROB_KIRA=0.1
+PROB_UNIQUE=0.0001
+
+# Unique card settings
+MAX_UNIQUE_CARDS=1000
+
+# CORS
+CORS_ORIGINS=["http://localhost:3000", "https://card.syui.ai"]
+
+# Security
+SECRET_KEY=your-secret-key-change-this-in-production