fix(transcription): auto-capture quote on text selection, smart comment button

- Quote captured automatically on mouseup in textarea (no button needed)
  Selection is held in state and pre-fills the comment input
- "Kommentieren" button only shown when zero comments exist
  When comments are present, the input is already visible — button is noise
- Chat bubble icon added to Kommentieren button for visual consistency

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

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

@@ -114,20 +114,9 @@ describe('TranscriptionBlock — interactions', () => {
 		expect(onFocus).toHaveBeenCalled();
 	});
 
-	it('shows Kommentieren button that opens comment thread', async () => {
+	it('shows Kommentieren button when no comments exist', async () => {
 		renderBlock();
 		const btn = page.getByText('Kommentieren');
 		await expect.element(btn).toBeInTheDocument();
 	});
-
-	it('shows quote hint when block is active', async () => {
-		renderBlock({ active: true });
-		await expect.element(page.getByText('Text markieren für Zitat')).toBeInTheDocument();
-	});
-
-	it('hides quote hint when block is not active', async () => {
-		renderBlock({ active: false });
-		const hint = page.getByText('Text markieren für Zitat');
-		await expect.element(hint).not.toBeInTheDocument();
-	});
 });