feat: improve editor localization and element editing workflow

[vigstudio]

Goal

This PR improves the editor’s element-editing workflow, completes Vietnamese localization coverage in core editor surfaces, and adds a fully offline image background-removal flow.

Scope of Changes

1) Editor Localization Improvements

• Reviewed and updated user-facing editor labels/messages for better Vietnamese consistency.
• Aligned context-menu actions and editor control labels.
• Updated locale message usage to reduce mixed-language UI states.

2) Fully Offline Background Removal

• Added local hosting flow for background-removal assets (no external API dependency).
• Configured runtime to use local model/resources in the current environment.
• Ensured middleware/routing behavior does not break local asset loading.

3) Background Removal on Selected Image Layer

• Fixed behavior so background removal applies to the currently selected image element, not only the primary photo.
• Added restore-original flow for processed layers.
• Preserved expected behavior for the main-photo fallback path.

4) Dedicated Element Edit Panel

• Added a dedicated element edit UI opened directly from element context actions.
• Moved to a left-side docked panel to avoid blocking the canvas preview.
• Included controls for:
  • Position (X/Y)
  • Size (W/H)
  • Rotation
  • Opacity
  • Visibility toggle
  • Lock/unlock
  • Delete element

5) Advanced Image Editing: Crop + Fill

• Added per-edge crop controls to remove extra/unwanted parts.
• Added image fill modes:
  • None
  • Solid color
  • Gradient
• Added fill intensity control.
• Fixed fill behavior to follow the image alpha/mask so fill affects actual image content, not the full element bounding box.

6) Preview and Export Rendering Sync

• Updated both live canvas preview rendering and export rendering paths.
• Ensured crop/fill/opacity/transform edits are consistently reflected in exported output.

7) Context Menu and Element Targeting Reliability

• Improved right-click target resolution for canvas elements.
• Reduced action mismatches caused by stale/async selection state.

Validation

• Type check:
  • docker compose exec app pnpm exec tsc -p tsconfig.json --noEmit

Outcome

• Element-level image editing is now more practical and precise.
• Background removal works offline and on the correct selected layer.
• Fill/crop behave correctly on real image detail regions.
• Editor language experience is more consistent for Vietnamese users.

Risks / Notes

• This PR touches UI + render/export logic across multiple editor surfaces; careful regression review is recommended.
• Offline asset bundle is large, so clone/pull and CI artifact transfer may take longer.

[CristianOlivera1]

I review it and validate it, Thanks !