feat(02): controller UI — vertical anim list, play/pause, browser audio, terminal aesthetic

- Replace waveform+DAW layout with animation controller
- Animations as vertical list with > cursor, no icons
- Transport: play/pause button, seek slider, time display
- Browser <audio> handles playback, 10Hz ticks to server
- Sidebar: devices only (200px)
- python:3.11-slim base (replaces Alpine, fixes librosa/numba build)
- libsndfile symlink kept for soundfile
- Remove python-mpv, add librosa for beat detection

Dockerfile

@@ -1,13 +1,12 @@
-FROM python:3.11-alpine
+FROM python:3.11-slim
 
 WORKDIR /app
 
-# Audio stack: ffmpeg for MP3 waveform + librosa, libsndfile for soundfile
-RUN apk add --no-cache \
+# ffmpeg for librosa audio decoding, libsndfile for soundfile
+RUN apt-get update && apt-get install -y --no-install-recommends \
     ffmpeg \
-    ffmpeg-libs \
-    libsndfile && \
-    ln -sf /usr/lib/libsndfile.so.1 /usr/lib/libsndfile.so
+    libsndfile1 && \
+    rm -rf /var/lib/apt/lists/*
 
 COPY pyproject.toml .
 RUN pip install --no-cache-dir .