feat(waveform): precompute and store peaks in DB for instant rendering

Store waveform peaks inline in audio_versions (JSONB columns) so WaveSurfer
can render the waveform immediately on page load without waiting for audio
decode. Adds a 100-point mini-waveform for version selector thumbnails.

Backend:
- Migration 0006: adds waveform_peaks and waveform_peaks_mini JSONB columns
- Worker generates both resolutions (500-pt full, 100-pt mini) during transcode
  and stores them directly in DB — replaces file-based waveform_url approach
- AudioVersionRead schema exposes both fields inline (no extra HTTP round-trip)
- GET /versions/{id}/waveform reads from DB; adds ?resolution=mini support

Frontend:
- audioService.initialize() accepts peaks and calls ws.load(url, Float32Array)
  so waveform renders instantly without audio decode
- useWaveform hook threads peaks option through to audioService
- PlayerPanel passes waveform_peaks from the active version to the hook
- New MiniWaveform SVG component (no WaveSurfer) renders mini peaks in the
  version selector buttons

Fix: docker-compose.dev.yml now runs alembic upgrade head before starting
the API server, so a fresh volume gets the full schema automatically.

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

api/alembic/versions/0006_waveform_peaks_in_db.py

@@ -0,0 +1,35 @@
+"""Store waveform peaks inline in audio_versions table.
+
+Replaces file-based waveform_url approach with two JSONB columns:
+- waveform_peaks: 500-point peaks for the player (passed directly to WaveSurfer)
+- waveform_peaks_mini: 100-point peaks for library/overview mini-waveform SVG
+
+Revision ID: 0006_waveform_peaks_in_db
+Revises: 0005_comment_tag
+Create Date: 2026-04-10
+"""
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects.postgresql import JSONB
+
+revision = "0006_waveform_peaks_in_db"
+down_revision = "0005_comment_tag"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "audio_versions",
+        sa.Column("waveform_peaks", JSONB, nullable=True),
+    )
+    op.add_column(
+        "audio_versions",
+        sa.Column("waveform_peaks_mini", JSONB, nullable=True),
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("audio_versions", "waveform_peaks_mini")
+    op.drop_column("audio_versions", "waveform_peaks")