docs: Add Redis/Valkey analysis and gitignore auto-generated files

Add comprehensive analysis of Redis/Valkey caching layer requirements.
Conclusion: not needed at current scale, but architecture is ready.

Also add gitignore pattern for auto-generated claude-mem context files
in subdirectories while preserving root CLAUDE.md.

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

Author: russellbrenner

.gitignore

@@ -23,4 +23,8 @@ __pycache__
 test
 *.db
 hits.json
-debug_*.log
+debug_*.log
+
+# Auto-generated claude-mem context files (but not root CLAUDE.md)
+**/CLAUDE.md
+!CLAUDE.md