feat(database): React entity UI components + columns metadata route

[ditadi]

🥞 Stacked PR

Use this link to review incremental changes.

• stack/database/foundation [Files changed]
  • stack/database/server [Files changed]
    • stack/database/brownfield [Files changed]
      • stack/database/init [Files changed]
        • stack/database/frontend [Files changed]
          • stack/database/ui [Files changed]
            • stack/database/advanced [Files changed]
              • stack/database/release [Files changed]

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Summary

React UI layer: entity table, mutation dialog, form helpers — plus the _columns/_entities routes and shared ColumnInfo source of truth.

• React entity components (view-entity, entity-form, entity-mutation-dialog)
• _columns and _entities routes (gated by HttpAccess)
• Omit private columns from _columns metadata
• Unify ColumnInfo in @databricks/shared (no more duplicate definitions)
• Wire column registry from typegen
• Refactor type generator (drop virtual module)

Stack (6/8)

1. #354 foundation
2. #355 server
3. #356 brownfield
4. #357 init
5. #358 frontend
6. ui ← this PR
7. advanced
8. release

Test plan

• biome check
• typecheck
• vitest (entity-form + view-entity tests pass)