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/lib/types/generation.ts

@@ -0,0 +1,34 @@
+export type GenerationStatus = "generating" | "complete" | "error" | "cancelled";
+
+export interface GenerationJob {
+  id: string;
+  created_at: string;
+  status: GenerationStatus;
+  script: string;
+  speaker: string;
+  cfg_scale: number;
+  inference_steps: number | null;
+  duration_secs: number | null;
+  sample_rate: number | null;
+  audio_path: string | null;
+  waveform_path: string | null;
+  error_message: string | null;
+}
+
+export interface WaveformPeaks {
+  sampleRate: number;
+  durationSecs: number;
+  channels: number;
+  samplesPerPixel: number;
+  length: number;
+  data: {
+    min: number[];
+    max: number[];
+  };
+}
+
+export interface GenerationsListResponse {
+  items: GenerationJob[];
+  limit: number;
+  offset: number;
+}