Refactor: Code cleanup and localStorage consolidation

This commit includes comprehensive codebase cleanup and refactoring:

## Code Cleanup
- Remove dead TypeScript code (types/monitoring.ts - 194 lines duplicate)
- Remove unused Go functions (GetClusterNodes, MigratePassword, GetClusterHealthInfo)
- Clean up commented-out code blocks across multiple files
- Remove unused TypeScript exports (helpTextClass, private tag color helpers)
- Delete obsolete test files and components

## localStorage Consolidation
- Centralize all storage keys into STORAGE_KEYS constant
- Update 5 files to use centralized keys:
  * utils/apiClient.ts (AUTH, LEGACY_TOKEN)
  * components/Dashboard/Dashboard.tsx (GUEST_METADATA)
  * components/Docker/DockerHosts.tsx (DOCKER_METADATA)
  * App.tsx (PLATFORMS_SEEN)
  * stores/updates.ts (UPDATES)
- Benefits: Single source of truth, prevents typos, better maintainability

## Previous Work Committed
- Docker monitoring improvements and disk metrics
- Security enhancements and setup fixes
- API refactoring and cleanup
- Documentation updates
- Build system improvements

## Testing
- All frontend tests pass (29 tests)
- All Go tests pass (15 packages)
- Production build successful
- Zero breaking changes

Total: 186 files changed, 5825 insertions(+), 11602 deletions(-)

go.mod

@@ -12,7 +12,6 @@ require (
 	github.com/gorilla/websocket v1.5.3
 	github.com/joho/godotenv v1.5.1
 	github.com/oklog/ulid/v2 v2.1.1
-	github.com/pkg/errors v0.9.1
 	github.com/prometheus/client_golang v1.23.2
 	github.com/rs/zerolog v1.34.0
 	github.com/shirou/gopsutil/v4 v4.25.9
@@ -53,6 +52,7 @@ require (
 	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
 	github.com/opencontainers/go-digest v1.0.0 // indirect
 	github.com/opencontainers/image-spec v1.1.1 // indirect
+	github.com/pkg/errors v0.9.1 // indirect
 	github.com/power-devops/perfstat v0.0.0-20240221224432-82ca36839d55 // indirect
 	github.com/prometheus/client_model v0.6.2 // indirect
 	github.com/prometheus/common v0.66.1 // indirect