feat(api): streaming, transcoding, events, history and likes (M3)

- tracks carry a stream_url signed for the user for 12 h and the
  user's reaction; /stream checks the signature, expiry and that the
  user is not blocked, then hands the file to nginx by X-Accel-Redirect
  (or serves it with Range support when X_ACCEL=false)
- original by default; formats browsers can't play and explicit
  high/medium/low go through Opus transcoding, never upwards: a lossy
  source under the target bitrate stays original; transcodes are
  cached per file and size, deduplicated in flight, limited by
  TRANSCODE_CONCURRENCY and trimmed hourly by LRU to the size limit
- /events takes up to 500 events with client UUIDs, drops repeats and
  events older than 30 days, counts plays (≥ half or 4 min, or
  finished), early skips and history entries (≥ 30 s)
- history with clearing, likes and dislikes with cursors and totals,
  track reactions, playback state with last-write-wins, tracks batch

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

services/api/cmd/api/main.go

@@ -9,9 +9,11 @@ import (
 	"os"
 	"os/signal"
 	"path/filepath"
+	"runtime"
 	"syscall"
 	"time"
 
+	"github.com/google/uuid"
 	"github.com/jackc/pgx/v5/pgxpool"
 	"github.com/redis/go-redis/v9"
 
@@ -22,6 +24,7 @@ import (
 	"pipu/api/internal/platform/db"
 	"pipu/api/internal/platform/httpx"
 	"pipu/api/internal/platform/sign"
+	"pipu/api/internal/playback"
 	"pipu/api/internal/search"
 	"pipu/api/internal/server"
 	"pipu/api/internal/system"
@@ -105,6 +108,25 @@ func run() error {
 		indexer.Trigger()
 	}
 	go covers.Run(ctx) // альбомы, оставшиеся без обложки с прошлого запуска
+
+	concurrency := cfg.TranscodeConcurrency
+	if concurrency <= 0 {
+		concurrency = max(1, runtime.NumCPU()/2)
+	}
+	transcoder := playback.NewTranscoder(cfg.FFmpegPath, filepath.Join(cfg.CacheDir, "transcode"), concurrency,
+		cfg.TranscodeCacheLimitGB, log)
+	go transcoder.RunCleanup(ctx)
+	rootFor := func(ctx context.Context, sourceID uuid.UUID) (string, error) {
+		src, err := libStore.GetSource(ctx, sourceID)
+		if err != nil {
+			return "", err
+		}
+		return libSvc.Root(src)
+	}
+	var dto library.DTO
+	pb := playback.NewHandler(playback.NewStore(pool), libStore, func() library.DTO { return dto }, signer, transcoder,
+		rootFor, cfg.XAccel, log)
+	dto = library.DTO{Signer: signer, Personal: pb}
 	libSvc.OnCatalogChanged = indexer.Trigger
 	indexer.Trigger() // индекс мог отстать (новая версия, сбой Meilisearch) — пересобираем при старте
 	go libSvc.Restore(ctx)
@@ -115,8 +137,9 @@ func run() error {
 		System:      sys,
 		Auth:        auth.NewHandler(authSvc, cfg.CookieSecure),
 		AuthService: authSvc,
-		Library:     library.NewHandler(libSvc, libStore, signer, covers, cfg.XAccel),
-		Search:      search.NewHandler(meili, libStore, indexer, library.DTO{Signer: signer}, log),
+		Library:     library.NewHandler(libSvc, libStore, dto, covers, cfg.XAccel),
+		Search:      search.NewHandler(meili, libStore, indexer, dto, log),
+		Playback:    pb,
 	}))
 	log.Info("starting", "version", buildinfo.Version)
 	return httpx.Serve(ctx, log, srv, cfg.ShutdownTimeout)