docs(memory-management): add comprehensive memory management concept page with tests

- Add complete memory management documentation covering:
  - Memory lifecycle (allocate, use, release)
  - Stack vs heap allocation with visual diagrams
  - Garbage collection and mark-and-sweep algorithm
  - Common memory leak patterns with fixes
  - WeakMap, WeakSet, and WeakRef usage
  - Chrome DevTools memory profiling guide
  - Best practices for memory-efficient code
- Add 34 tests covering memory allocation, references, WeakMap/WeakSet,
  memory leak patterns, object pools, and cleanup patterns
- Include 4 MDN references, 4 articles, and 4 video resources
- SEO optimized: 4,420 words, 30/30 SEO score