feat: read-only content view for data table records, edit on demand

[esafwan]

Summary

• DataRecordViewPage.tsx now defaults to a read-only, well-formatted "content view" when opening a record — fields are grouped in a <Card> with proper depth/structure instead of a flat wall of always-editable inputs.
• Adds an explicit "Edit" button; editing reuses the existing form/save logic unchanged, just gated behind an edit-mode toggle. Cancel/Back from edit mode discards unsaved changes and returns to content view.
• Fixes DataRecordFormLayout.tsx design-token violations (hardcoded #000000 color fallback, raw <Label>/<Input> where shadcn form primitives should be used).
• Sensible read-only rendering per field type: booleans render as Yes/No badges, Select/status fields as badges, dates formatted, long text preserves whitespace.

Screenshots (live bench)

Content view (default):

Edit mode (on demand):

Test plan

• yarn typecheck — 0 errors
• yarn lint — 0 errors (60 pre-existing unrelated warnings)
• Verified live on bench (huf.localhost): content view renders by default, Edit button switches to the existing form, Cancel discards changes

[esafwan]

Superseded by consolidated Data Tables PR #460, now included in integration PR #468.