fix(infra): add POCKET_TTS_URL to backend and runner services

Backend was missing POCKET_TTS_URL entirely — pocketTTSClient was nil
so voices() only returned 67 Kokoro voices. Runner already had the var
via Doppler but it was absent from the compose environment block.

Also fix stray leading space on backend environment: key (YAML parse error).

Verified: /api/voices now returns 87 voices (67 kokoro + 20 pocket-tts).

docker-compose.yml

@@ -154,7 +154,7 @@ services:
     # No public port — all traffic is routed via Caddy.
     expose:
       - "8080"
-     environment:
+    environment:
       <<: *infra-env
       BACKEND_HTTP_ADDR: ":8080"
       LOG_LEVEL: "${LOG_LEVEL}"
@@ -224,6 +224,7 @@ services:
       # Kokoro-FastAPI TTS endpoint
       KOKORO_URL: "${KOKORO_URL}"
       KOKORO_VOICE: "${KOKORO_VOICE}"
+      POCKET_TTS_URL: "${POCKET_TTS_URL}"
       GLITCHTIP_DSN: "${GLITCHTIP_DSN}"
       OTEL_EXPORTER_OTLP_ENDPOINT: "${OTEL_EXPORTER_OTLP_ENDPOINT}"
       OTEL_SERVICE_NAME: "runner"