Add Data Explorer tab for database browsing

[thekevinm]

Summary

• Adds a new Data Explorer tab under "API Generation & Connections" that provides a DBeaver-like database management experience for non-technical users
• Three-panel layout: database API selector → schema/table tree navigator → read-only data grid with pagination, sorting, filtering, and search
• Performance-optimized: lazy loading at every level — no data fetched until user explicitly selects a database, table, etc.

New Components

• DfDataExplorerComponent — Main container with resizable sidebar
• DfDbSelectorComponent — Lists database-type APIs for selection
• DfSchemaTreeComponent — Tree view of tables from /_schema endpoint
• DfDataGridComponent — Paginated data table (50 rows/page) with column sorting, global search, and column filter
• DataExplorerService — Service layer wrapping all API calls

Key Design Decisions

• Read-only for initial release (no insert/update/delete)
• Server-side pagination via limit/offset query params to handle large tables
• Lazy schema loading — _schema only called when user clicks a database API
• Standalone components following existing DreamFactory patterns (@UntilDestroy, df- prefix)
• Full i18n support with dedicated dataExplorer translation scope

Test plan

• Verify "Data Explorer" tab appears under API Generation & Connections in sidebar
• Click a database API and confirm schema/tables load in tree view
• Select a table and verify data displays in paginated grid
• Test pagination (next/previous/page size changes)
• Test column sorting (click column headers)
• Test search/filter functionality
• Verify empty states (no databases, no tables, no data)
• Confirm no performance issues with large tables (pagination prevents full load)
• Check responsive layout and theme consistency with existing UI

🤖 Generated with Claude Code