Wire the full text-style chain so selecting a text clip lets the user
change font, size, color, alignment, background, border, and shadow in
the Inspector, with the change re-rasterizing live.

The domain `TextStyle` and the render `CosmicTextRasterizer` already
supported these; the missing link was a command/IPC path to write
`clip.text_style`, and a UI beyond the plain text box.

- ops: add `text_style: Option<TextStyle>` to `ClipProperties`, written
  in `apply_property_changes` (reuses the existing `SetClipProperties`
  transaction → undo/redo/version for free). Two unit tests.
- ipc: add `textStyle` to `ClipPropertiesDto` (camelCase, `serde(default)`)
  and map it through; serde regression test.
- types: add `textStyle?: TextStyle` to `ClipPropertiesReq`.
- inspector: TextTab gains font family / size (scrubbable) / color /
  alignment / background / border / shadow controls, reusing
  ScrubbableNumberField + the color-swatch pattern. New i18n keys (zh/en).
- The `SetClipProperties` payload (ops enum + IPC DTO) is now boxed:
  `TextStyle` makes `ClipProperties` large enough to trip clippy's
  large_enum_variant, and the enum is cloned on every undo snapshot.

Render needs no change: text resolves by clip_id and reads the live
`text_style` at composite time.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>