feat(phase-1): persistent generation library

- Save every completed generation to SQLite (generation_store.py) with
  WAV and waveform peaks written to data/generations/<id>/
- Deferred DB write until success — cancelled/errored generations never
  touch the DB and never appear in the library
- Fixed cancel+regenerate IndexError: _reset_scheduler_caches() now
  directly zeros scheduler._step_index and running state in addition to
  clearing VibePod cache dicts; same explicit resets added in the fresh
  path of prepare_noise_scheduler as belt-and-suspenders
- Added /library page with GenerationCard, WaveformPreview, waveform
  fetch, play/pause, download, delete, pagination, empty + error states
- Added generation API routes (list, single, audio stream, waveform,
  delete) proxying to Python server
- Added Library nav link to Header with active state
- Persist script/speaker/CFG to localStorage so generate page state
  survives navigation
- Updated build plan: Phase 0+1 ticked off, better-sqlite3 moved to
  Phase 2, architectural note on Python owning all persistence

web/components/WaveformPreview.tsx

@@ -0,0 +1,57 @@
+"use client";
+
+import { useEffect, useRef } from "react";
+import type { WaveformPeaks } from "@/lib/types/generation";
+
+interface WaveformPreviewProps {
+  peaks: WaveformPeaks;
+  color?: string;
+  height?: number;
+  className?: string;
+}
+
+export default function WaveformPreview({
+  peaks,
+  color = "#2dd4bf",
+  height = 48,
+  className = "",
+}: WaveformPreviewProps) {
+  const canvasRef = useRef<HTMLCanvasElement>(null);
+
+  useEffect(() => {
+    const canvas = canvasRef.current;
+    if (!canvas) return;
+
+    const ctx = canvas.getContext("2d");
+    if (!ctx) return;
+
+    const { width } = canvas;
+    const midY = height / 2;
+    const { min, max } = peaks.data;
+    const len = peaks.length;
+
+    ctx.clearRect(0, 0, width, height);
+    ctx.strokeStyle = color;
+    ctx.lineWidth = 1;
+
+    for (let x = 0; x < width; x++) {
+      const peakIndex = Math.floor((x / width) * len);
+      const minY = midY - min[peakIndex] * midY;
+      const maxY = midY - max[peakIndex] * midY;
+      ctx.beginPath();
+      ctx.moveTo(x + 0.5, Math.min(minY, maxY));
+      ctx.lineTo(x + 0.5, Math.max(minY, maxY));
+      ctx.stroke();
+    }
+  }, [peaks, color, height]);
+
+  return (
+    <canvas
+      ref={canvasRef}
+      width={400}
+      height={height}
+      className={`w-full ${className}`}
+      style={{ height }}
+    />
+  );
+}