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/internal/runner/runner.go

@@ -22,6 +22,10 @@ import (
 	"sync/atomic"
 	"time"
 
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/codes"
+
 	"github.com/libnovel/backend/internal/bookstore"
 	"github.com/libnovel/backend/internal/domain"
 	"github.com/libnovel/backend/internal/kokoro"
@@ -301,6 +305,14 @@ func (r *Runner) newOrchestrator() *orchestrator.Orchestrator {
 
 // runScrapeTask executes one scrape task end-to-end and reports the result.
 func (r *Runner) runScrapeTask(ctx context.Context, task domain.ScrapeTask) {
+	ctx, span := otel.Tracer("runner").Start(ctx, "runner.scrape_task")
+	defer span.End()
+	span.SetAttributes(
+		attribute.String("task.id", task.ID),
+		attribute.String("task.kind", task.Kind),
+		attribute.String("task.url", task.TargetURL),
+	)
+
 	log := r.deps.Log.With("task_id", task.ID, "kind", task.Kind, "url", task.TargetURL)
 	log.Info("runner: scrape task starting")
 
@@ -340,8 +352,10 @@ func (r *Runner) runScrapeTask(ctx context.Context, task domain.ScrapeTask) {
 
 	if result.ErrorMessage != "" {
 		r.tasksFailed.Add(1)
+		span.SetStatus(codes.Error, result.ErrorMessage)
 	} else {
 		r.tasksCompleted.Add(1)
+		span.SetStatus(codes.Ok, "")
 	}
 
 	log.Info("runner: scrape task finished",
@@ -384,6 +398,15 @@ func (r *Runner) runCatalogueTask(ctx context.Context, task domain.ScrapeTask, o
 
 // runAudioTask executes one audio-generation task.
 func (r *Runner) runAudioTask(ctx context.Context, task domain.AudioTask) {
+	ctx, span := otel.Tracer("runner").Start(ctx, "runner.audio_task")
+	defer span.End()
+	span.SetAttributes(
+		attribute.String("task.id", task.ID),
+		attribute.String("book.slug", task.Slug),
+		attribute.Int("chapter.number", task.Chapter),
+		attribute.String("audio.voice", task.Voice),
+	)
+
 	log := r.deps.Log.With("task_id", task.ID, "slug", task.Slug, "chapter", task.Chapter, "voice", task.Voice)
 	log.Info("runner: audio task starting")
 
@@ -407,6 +430,7 @@ func (r *Runner) runAudioTask(ctx context.Context, task domain.AudioTask) {
 	fail := func(msg string) {
 		log.Error("runner: audio task failed", "reason", msg)
 		r.tasksFailed.Add(1)
+		span.SetStatus(codes.Error, msg)
 		result := domain.AudioResult{ErrorMessage: msg}
 		if err := r.deps.Consumer.FinishAudioTask(ctx, task.ID, result); err != nil {
 			log.Error("runner: FinishAudioTask failed", "err", err)
@@ -441,6 +465,7 @@ func (r *Runner) runAudioTask(ctx context.Context, task domain.AudioTask) {
 	}
 
 	r.tasksCompleted.Add(1)
+	span.SetStatus(codes.Ok, "")
 	result := domain.AudioResult{ObjectKey: key}
 	if err := r.deps.Consumer.FinishAudioTask(ctx, task.ID, result); err != nil {
 		log.Error("runner: FinishAudioTask failed", "err", err)