feat: add 33 skills from vudovn/antigravity-kit

- Added: api-patterns, app-builder, architecture, bash-linux, behavioral-modes,
  clean-code, code-review-checklist, database-design, deployment-procedures,
  docker-expert, documentation-templates, game-development, geo-fundamentals,
  i18n-localization, lint-and-validate, mobile-design, nestjs-expert,
  nextjs-best-practices, nodejs-best-practices, parallel-agents,
  performance-profiling, plan-writing, powershell-windows, prisma-expert,
  python-patterns, react-patterns, red-team-tactics, seo-fundamentals,
  server-management, tailwind-patterns, tdd-workflow, typescript-expert,
  vulnerability-scanner
- Updated README: skill count 179 → 223
- Added credit for vudovn/antigravity-kit (MIT License)

Source: https://github.com/vudovn/antigravity-kit

skills/database-design/database-selection.md

@@ -0,0 +1,43 @@
+# Database Selection (2025)
+
+> Choose database based on context, not default.
+
+## Decision Tree
+
+```
+What are your requirements?
+│
+├── Full relational features needed
+│   ├── Self-hosted → PostgreSQL
+│   └── Serverless → Neon, Supabase
+│
+├── Edge deployment / Ultra-low latency
+│   └── Turso (edge SQLite)
+│
+├── AI / Vector search
+│   └── PostgreSQL + pgvector
+│
+├── Simple / Embedded / Local
+│   └── SQLite
+│
+└── Global distribution
+    └── PlanetScale, CockroachDB, Turso
+```
+
+## Comparison
+
+| Database | Best For | Trade-offs |
+|----------|----------|------------|
+| **PostgreSQL** | Full features, complex queries | Needs hosting |
+| **Neon** | Serverless PG, branching | PG complexity |
+| **Turso** | Edge, low latency | SQLite limitations |
+| **SQLite** | Simple, embedded, local | Single-writer |
+| **PlanetScale** | MySQL, global scale | No foreign keys |
+
+## Questions to Ask
+
+1. What's the deployment environment?
+2. How complex are the queries?
+3. Is edge/serverless important?
+4. Vector search needed?
+5. Global distribution required?