improve GUI layout and LRC stage controls

- make the main page scrollable and keep the console reachable on small screens
- add fullscreen toggle (button + F11, Escape to exit)
- add enable switches for LRC generation/embedding and skip ready text.lrc
- sanitize multi-line ASR text before writing LRC timestamps
- emit LRC/embed progress once per file instead of twice
- increase progress-bar contrast

core/lrc.py

@@ -37,6 +37,10 @@ def segments_to_lrc(segments: list[dict]) -> str:
         text = (seg.get("text") or "").strip()
         if not text:
             continue
+        # WhisperX can return multi-line text on long segments. An LRC line
+        # must be a single line: any newline would produce a broken line
+        # without a timestamp. Collapse all whitespace into single spaces.
+        text = re.sub(r"\s+", " ", text)
         start = float(seg.get("start", 0.0))
         lines.append(f"{format_timestamp(start)}{text}")
     return "\n".join(lines) + "\n"