feat(telemetry): add caching, alerts, migration & dashboard improvements

- Add Redis/in-memory caching layer (cache.go)
- Add SMTP alerting for high failure rates (alerts.go)
- Add data migration script from old API (migrate.go)
- Add docker-compose.yml for easy deployment
- Move dashboard to / with redirect from /dashboard
- Add dark/light mode toggle
- Add error analysis and failed apps statistics
- Add PVE version and LXC/VM type stats
- Add /metrics Prometheus endpoint
- Add /api/records pagination endpoint
- Add CSV export functionality
- Enhanced healthcheck with PB connection status

New ENV vars:
- Cache: ENABLE_CACHE, CACHE_TTL_SECONDS, ENABLE_REDIS, REDIS_URL
- Alerts: ALERT_ENABLED, SMTP_*, ALERT_FAILURE_THRESHOLD, etc.
- Migration: RUN_MIGRATION, MIGRATION_REQUIRED, MIGRATION_SOURCE_URL

misc/data/Dockerfile

@@ -1,10 +1,52 @@
 FROM golang:1.25-alpine AS build
 WORKDIR /src
+COPY go.mod go.sum* ./
+RUN go mod download 2>/dev/null || true
 COPY . .
 RUN go build -trimpath -ldflags "-s -w" -o /out/telemetry-ingest .
+RUN go build -trimpath -ldflags "-s -w" -o /out/migrate migrate.go
 
 FROM alpine:3.23
+RUN apk add --no-cache ca-certificates tzdata
 WORKDIR /app
 COPY --from=build /out/telemetry-ingest /app/telemetry-ingest
+COPY --from=build /out/migrate /app/migrate
+COPY entrypoint.sh /app/entrypoint.sh
+RUN chmod +x /app/entrypoint.sh /app/migrate
+
+# Service config
+ENV LISTEN_ADDR=":8080"
+ENV MAX_BODY_BYTES="1024"
+ENV RATE_LIMIT_RPM="60"
+ENV RATE_BURST="20"
+ENV UPSTREAM_TIMEOUT_MS="4000"
+ENV ENABLE_REQUEST_LOGGING="false"
+
+# Cache config (optional)
+ENV ENABLE_CACHE="true"
+ENV CACHE_TTL_SECONDS="60"
+ENV ENABLE_REDIS="false"
+# ENV REDIS_URL="redis://localhost:6379"
+
+# Alert config (optional)
+ENV ALERT_ENABLED="false"
+# ENV SMTP_HOST=""
+# ENV SMTP_PORT="587"
+# ENV SMTP_USER=""
+# ENV SMTP_PASSWORD=""
+# ENV SMTP_FROM="telemetry@proxmoxved.local"
+# ENV SMTP_TO=""
+# ENV SMTP_USE_TLS="false"
+ENV ALERT_FAILURE_THRESHOLD="20.0"
+ENV ALERT_CHECK_INTERVAL_MIN="15"
+ENV ALERT_COOLDOWN_MIN="60"
+
+# Migration config (optional)
+ENV RUN_MIGRATION="false"
+ENV MIGRATION_REQUIRED="false"
+ENV MIGRATION_SOURCE_URL="https://api.htl-braunau.at/dev/data"
+
 EXPOSE 8080
-CMD ["/app/telemetry-ingest"]
+HEALTHCHECK --interval=30s --timeout=3s --start-period=5s \
+    CMD wget -q --spider http://localhost:8080/healthz || exit 1
+ENTRYPOINT ["/app/entrypoint.sh"]