refactor(auth): replace in-memory auth cache with Redis

[ben-fornefeld]

Summary

• Replaces the in-memory MemoryCache in AuthCache with RedisCache so auth cache invalidation is correct across all service instances
• Both API and dashboard-API now share a Redis-backed auth cache (prefix auth:team) with 5m TTL and 1m background refresh
• Wires Redis config (URL, cluster URL, TLS CA) into the dashboard-API's Nomad job via Terraform

Changes

• packages/auth/pkg/auth/cache.go — NewAuthCache now takes a redis.UniversalClient; uses RedisCache directly
• packages/api/internal/handlers/store.go — passes existing redisClient to NewAuthCache
• packages/dashboard-api/main.go — creates Redis client via factories.NewRedisClient
• packages/dashboard-api/internal/cfg/model.go — adds RedisURL, RedisClusterURL, RedisTLSCABase64
• iac/modules/job-dashboard-api/ — adds Redis variables and env vars to Nomad job
• iac/provider-gcp/nomad/main.tf — passes Redis config to dashboard-api module

Test plan

• go build ./... passes for auth, api, and dashboard-api packages
• go test ./... passes for auth and dashboard-api packages
• Lint passes for all modified packages (pre-existing Linux-only failures unaffected)
• Verify Redis connectivity in staging after deploy

🤖 Generated with Claude Code

[cursor]

PR Summary

Medium Risk
Touches authentication caching and invalidation behavior across services and introduces a new runtime dependency on Redis configuration, so misconfiguration or Redis issues could impact auth checks and team membership changes.

Overview
This PR switches the shared auth/team cache from an in-memory implementation to a Redis-backed cache (with a shared auth:team prefix), updating cache invalidation APIs to be context-aware and wiring existing and new callers (API and dashboard-api) to pass a Redis client. It also makes dashboard-api require Redis configuration at startup, creates/cleans up a Redis client in main.go, and propagates Redis URL/cluster/TLS CA settings through Terraform/Nomad so deployments provide the needed env vars.

^{Written by Cursor Bugbot for commit 709f813. This will update automatically on new commits. Configure here.}