Add offline RefreshPrices, fix sync bugs, implement auto-restart

- Implement RefreshPrices for local-first mode
  - Update prices from local_components.current_price cache
  - Graceful degradation when component not found
  - Add PriceUpdatedAt timestamp to LocalConfiguration model
  - Support both authenticated and no-auth price refresh

- Fix sync duplicate entry bug
  - pushConfigurationUpdate now ensures server_id exists before update
  - Fetch from LocalConfiguration.ServerID or search on server if missing
  - Update local config with server_id after finding

- Add application auto-restart after settings save
  - Implement restartProcess() using syscall.Exec
  - Setup handler signals restart via channel
  - Setup page polls /health endpoint and redirects when ready
  - Add "Back" button on setup page when settings exist

- Fix setup handler password handling
  - Use PasswordEncrypted field consistently
  - Support empty password by using saved value

- Improve sync status handling
  - Add fallback for is_offline check in SyncStatusPartial
  - Enhance background sync logging with prefixes

- Update CLAUDE.md documentation
  - Mark Phase 2.5 tasks as complete
  - Add UI Improvements section with future tasks
  - Update SQLite tables documentation

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

internal/localdb/models.go

@@ -69,6 +69,7 @@ type LocalConfiguration struct {
 	Notes          string           `json:"notes"`
 	IsTemplate     bool             `gorm:"default:false" json:"is_template"`
 	ServerCount    int              `gorm:"default:1" json:"server_count"`
+	PriceUpdatedAt *time.Time       `gorm:"type:timestamp" json:"price_updated_at,omitempty"`
 	CreatedAt      time.Time        `json:"created_at"`
 	UpdatedAt      time.Time        `json:"updated_at"`
 	SyncedAt       *time.Time       `json:"synced_at"`