Pull Request: Dynamic System Configuration & Multi-Tier Feature Flags

Summary

Implements a centralized System Configuration & Feature Flags Management system across both Backend and Frontend. This eliminates hardcoded business constants, allows runtime feature toggling, enables zero-downtime Firecrawl API key rotation, and dynamically feeds business quotas/rate-limits directly into active middleware and background workers.

Frontend Changes (data-crawler-fe)

1. Data Layer & Hooks

• Defined types in src/types/system-config.ts and singleton client in src/services/system-config.service.ts.
• Added TanStack Query hooks in src/hooks/use-system-config.ts:
  • usePublicConfigs() with helper isFeatureEnabled(key).
  • Admin management hooks: useSystemConfigsList, useCreateSystemConfig, useUpdateSystemConfig, useToggleFeatureFlag, useDeleteSystemConfig.

2. Organic Biophilic UI Components (src/components/system-config/)

• KPI Metrics: Total Configs, Active Feature Flags, Public Configs count.
• Unified Table Card: Compliant with workspace table standards, sortable columns, custom category badges, and inline boolean switches.
• Card Grid View: Responsive cards for mobile/touch-friendly view.
• Smart Modal: Dynamic input switching based on value type (Boolean switch, Number input, String input, JSON code editor).
• Safe Deletion Dialog: Prevents accidental deletion of vital keys.

3. Navigation, Guards & UX

• Added page routes:
  • /settings/developer/system-configs (Developer Shell tab).
  • /system-configs (Standalone page with SEO metadata).
• Registered routes in ADMIN_ROUTES within Next.js middleware.ts.
• Added dynamic notice & disabled state to src/app/(auth)/register/page.tsx when registration is disabled.
• Full bilingual coverage (English & Vietnamese) in translations.ts.