fix(backend): make sentry traces-sample-rate env-configurable

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.env.example

@@ -50,6 +50,7 @@ GLITCHTIP_SECRET_KEY=changeme-generate-a-real-secret
 # Error reporting DSNs — leave empty to disable the SDK (safe default).
 # SENTRY_DSN: backend (Spring Boot) — used by the GlitchTip/Sentry Java SDK
 SENTRY_DSN=
+SENTRY_TRACES_SAMPLE_RATE=
 # VITE_SENTRY_DSN: frontend (SvelteKit) — injected at build time via Vite
 VITE_SENTRY_DSN=
 # Sentry/GlitchTip auth token for source map upload at build time (optional)

backend/src/main/resources/application.yaml

@@ -122,7 +122,7 @@ ocr:
 sentry:
   dsn: ${SENTRY_DSN:}
   environment: ${SPRING_PROFILES_ACTIVE:dev}
-  traces-sample-rate: 1.0
+  traces-sample-rate: ${SENTRY_TRACES_SAMPLE_RATE:1.0}
   send-default-pii: false
   enable-tracing: true
   ignored-exceptions-for-type:

docker-compose.yml

@@ -148,6 +148,7 @@ services:
       APP_OCR_BASE_URL: http://ocr-service:8000
       APP_OCR_TRAINING_TOKEN: "${OCR_TRAINING_TOKEN:-}"
       SENTRY_DSN: ${SENTRY_DSN:-}
+      SENTRY_TRACES_SAMPLE_RATE: ${SENTRY_TRACES_SAMPLE_RATE:-1.0}
       # Observability: send traces to Tempo inside archiv-net (OTLP gRPC port 4317)
       # Tempo is defined in docker-compose.observability.yml (future issue).
       # OTLP failures are non-fatal — backend starts cleanly without the observability stack.