feat(rec): audio analyzer and My Wave v1 engine (M4)

- migration 00006: track features and embeddings (pgvector, HNSW),
  analysis queue filled by a trigger on new tracks, wave sessions and
  impressions, recommender profiles, model versions
- analyzer basic-1 (ADR-014): ffmpeg decode, three 30 s excerpts,
  256-d timbre/rhythm embedding, tempo by onset autocorrelation, key,
  loudness, energy, danceability, acousticness, intro length; worker
  with SKIP LOCKED claims, retries and re-analysis on version change
- wave engine v1: candidates (session/taste similarity, fresh,
  liked artists, rediscover, popular, exploration, seed), filters
  (dislikes, played in 3 h, already served), heuristic score, activity
  and mood fit from contexts.yaml with relaxing thresholds, MMR with
  one track per artist, exploration share, session vector updated by
  reactions and a change of course after three skips
- POST /internal/wave/batch with the catalog index cached in memory
  and the session kept in Redis

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

services/recommender/pipu_rec/settings.py

@@ -13,4 +13,8 @@ class Settings(BaseSettings):
     redis_url: str = Field(default="redis://redis:6379/0")
     internal_token: str = Field(default="", description="Общий секрет для вызовов из api")
     log_level: str = "info"
+    library_root: str = "/library"
+    library_host_root: str = "/library-host"
+    ffmpeg_path: str = "ffmpeg"
+    contexts_path: str = Field(default="", description="contexts.yaml; пусто — встроенный")
     version: str = Field(default="0.0.0-dev", alias="PIPU_VERSION")