Text effects, pad crossfade, playback progress + per-track durations

- Scrolling text: font, size, weight, colour and movement effects (up/down, wave,
  zoom, flash, rotate) rendered per-letter (and captured in recordings).
- Larger multiline text input.
- Pad bank: crossfade between pads (per-source gain ramps in the audio engine).
- Duration + remaining-time and progress bars for the playlist and the active pad,
  via metadata probing and live progress reports from the output window.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/output.html

@@ -18,7 +18,7 @@
   <img id="logo-1" class="logo" />
 
   <!-- Scrolling text ticker -->
-  <div id="ticker"><div id="ticker-track"><span></span><span></span></div></div>
+  <div id="ticker"><div id="ticker-track"><span class="tick-copy"></span><span class="tick-copy"></span></div></div>
 
   <div id="drop-hint">
     <div class="big">🎛 In attesa dell'audio…</div>