feat(datalayers-single): add postgres, redis, prometheus protocol support

[Rory-Z]

Summary

• Add optional PostgreSQL (5432), Redis (6379), and Prometheus (9090) protocol support to the datalayers-single Helm chart
• Each protocol is toggled via service.{postgres,redis,prometheus}.enabled in values.yaml (all disabled by default)
• When enabled, the chart injects the DATALAYERS_SERVER__*__ADDR env var, exposes the container port, and adds a Service port
• Redis credentials reuse the existing auth secret (auth.static)
• Prometheus tuning params (memtable_size, ttl) use Datalayers defaults, configurable via datalayersConfig TOML if needed

Reference: https://docs.datalayers.cn/datalayers/latest/development-guide/connection.html#端口说明

Changes

File	Change
values.yaml	Add service.postgres/redis/prometheus blocks
templates/statefulset.yaml	Conditional containerPorts + env vars
templates/service.yaml	Conditional Service ports
templates/NOTES.txt	Conditional port info, connect URLs, port-forward args

Test plan

• helm lint passes
• helm template with defaults — no protocol ports in output (unchanged behavior)
• helm template --set service.postgres.enabled=true — PostgreSQL port + env var present
• helm template --set service.redis.enabled=true — Redis port + ADDR/USERNAME/PASSWORD env vars present
• helm template --set service.prometheus.enabled=true — Prometheus port + env var present
• helm template with all three enabled — all ports and env vars present together