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/optimization.md

@@ -0,0 +1,36 @@
+# Query Optimization
+
+> N+1 problem, EXPLAIN ANALYZE, optimization priorities.
+
+## N+1 Problem
+
+```
+What is N+1?
+├── 1 query to get parent records
+├── N queries to get related records
+└── Very slow!
+
+Solutions:
+├── JOIN → Single query with all data
+├── Eager loading → ORM handles JOIN
+├── DataLoader → Batch and cache (GraphQL)
+└── Subquery → Fetch related in one query
+```
+
+## Query Analysis Mindset
+
+```
+Before optimizing:
+├── EXPLAIN ANALYZE the query
+├── Look for Seq Scan (full table scan)
+├── Check actual vs estimated rows
+└── Identify missing indexes
+```
+
+## Optimization Priorities
+
+1. **Add missing indexes** (most common issue)
+2. **Select only needed columns** (not SELECT *)
+3. **Use proper JOINs** (avoid subqueries when possible)
+4. **Limit early** (pagination at database level)
+5. **Cache** (when appropriate)