feat(comments): inline edit on click + trash icon for own comments

Own comments:
- Click the text to open inline edit (textarea replaces text)
- Enter saves, Escape cancels
- Small trash icon always visible in bottom-right corner
- Hover on text shows cursor-text + subtle bg highlight

Other people's comments: read-only, no edit/delete affordances.

Re-add currentUserId prop chain for ownership check.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/components/TranscriptionBlock.svelte.spec.ts

@@ -15,6 +15,7 @@ function renderBlock(overrides: Record<string, unknown> = {}) {
 		active: false,
 		saveState: 'idle' as const,
 		canComment: true,
+		currentUserId: 'user-1',
 		onTextChange: vi.fn(),
 		onFocus: vi.fn(),
 		onDeleteClick: vi.fn(),