chore: remove redundant files after .NET backend migration

- Removed old NestJS backend code (src/apps/tracker-api/src/)
- Removed old TypeScript libs (src/libs/domain, src/libs/discovery)
- Removed duplicated libs/ directory at root
- Removed .mimocode/ and .obsidian/ from tracking
- Removed .DS_Store files
- Added .mimocode/, .obsidian/, .DS_Store to .gitignore
- Removed empty placeholder directories (docs/audit/gaps, docs/audit/opportunities)
- Cleaned up tsconfig.base.json path aliases
- Removed stale Nx README

Author: beyondnetPeru

.DS_Store

@@ -145,6 +145,15 @@ vite.config.ts.timestamp-*
 # Claude Code local configuration
 .claude/
 
+# MiMo Code local configuration
+.mimocode/
+
+# Obsidian vault configuration
+.obsidian/
+
+# macOS metadata
+.DS_Store
+
 # Upstream submodule clone — never commit directly
 .evolith_arch32_tmp/
 .tmp/