feat(observability+tts): OTel logs for backend/runner/ui; add kokoro-fastapi (GPU) and pocket-tts (CPU) to homelab

- otelsetup.Init now returns a *slog.Logger wired to the OTLP log exporter
  so all slog output is shipped to Loki with embedded trace IDs
- backend and runner both adopt the new OTel-bridged logger
- runner.runScrapeTask and runAudioTask now emit structured OTel spans
- ui/hooks.server.ts adds BatchLogRecordProcessor alongside existing trace exporter
- homelab: add kokoro-fastapi GPU service (ghcr.io/remsky/kokoro-fastapi-gpu)
  using deploy.resources.reservations for NVIDIA GPU, exposed internally on :8880
- homelab: add pocket-tts CPU service (ghcr.io/kyutai-labs/pocket-tts) on :8000
- runner KOKORO_URL hardcoded to http://kokoro-fastapi:8880 (fixes DNS failure
  for the stale kokoro.kalekber.cc hostname)

backend/cmd/backend/main.go

@@ -71,14 +71,17 @@ func run() error {
 	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
 	defer stop()
 
-	// ── OpenTelemetry tracing ─────────────────────────────────────────────────
-	otelShutdown, err := otelsetup.Init(ctx, version)
+	// ── OpenTelemetry tracing + logs ──────────────────────────────────────────
+	otelShutdown, otelLog, err := otelsetup.Init(ctx, version)
 	if err != nil {
 		return fmt.Errorf("init otel: %w", err)
 	}
 	if otelShutdown != nil {
 		defer otelShutdown()
-		log.Info("otel tracing enabled", "endpoint", os.Getenv("OTEL_EXPORTER_OTLP_ENDPOINT"))
+		// Replace the plain slog logger with the OTel-bridged one so all
+		// structured log lines are forwarded to Loki with trace IDs attached.
+		log = otelLog
+		log.Info("otel tracing + logs enabled", "endpoint", os.Getenv("OTEL_EXPORTER_OTLP_ENDPOINT"))
 	}
 
 	// ── Storage ──────────────────────────────────────────────────────────────

backend/cmd/runner/main.go

@@ -25,6 +25,7 @@ import (
 	"github.com/libnovel/backend/internal/kokoro"
 	"github.com/libnovel/backend/internal/meili"
 	"github.com/libnovel/backend/internal/novelfire"
+	"github.com/libnovel/backend/internal/otelsetup"
 	"github.com/libnovel/backend/internal/runner"
 	"github.com/libnovel/backend/internal/storage"
 )
@@ -70,6 +71,19 @@ func run() error {
 	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
 	defer stop()
 
+	// ── OpenTelemetry tracing + logs ─────────────────────────────────────────
+	otelShutdown, otelLog, err := otelsetup.Init(ctx, version)
+	if err != nil {
+		return fmt.Errorf("init otel: %w", err)
+	}
+	if otelShutdown != nil {
+		defer otelShutdown()
+		// Switch to the OTel-bridged logger so all structured log lines are
+		// forwarded to Loki with trace IDs attached.
+		log = otelLog
+		log.Info("otel tracing + logs enabled", "endpoint", os.Getenv("OTEL_EXPORTER_OTLP_ENDPOINT"))
+	}
+
 	// ── Storage ─────────────────────────────────────────────────────────────
 	store, err := storage.NewStore(ctx, cfg, log)
 	if err != nil {