Expanded field types (Number, Email, Textarea, DateTime, Currency, Slug, Markdown, Tags, File, Color, KeyValue)

[eaguad1337]

Broaden the field catalog beyond the current set. Each new type needs a backend field + a frontend component + correct (de)serialization.

Targets: Number, Email, Textarea, DateTime, Currency, Slug, Markdown, Tags/MultiSelect, generic File (non-image), Color, KeyValue.

Acceptance: each new field renders in index/detail/forms and round-trips correctly.