fix: Redis client initialization at runtime vs build time

- Add `dynamic = 'force-dynamic'` to /api/build-info route to prevent
  static caching of runtime values (hostname, REDIS_URL, etc.)
- Fix Redis client singleton to retry initialization if REDIS_URL
  wasn't set at build time but is set at runtime
- Update Traefik health check from `/` to `/api/health` for better
  health checking (verifies database connectivity)

The issue was that Next.js was evaluating redis.ts at build time
(when REDIS_URL isn't set in Docker buildkit), caching `null` as the
client, and never re-checking at runtime. Now it retries if the env
var becomes available.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/web/src/app/api/build-info/route.ts

@@ -3,6 +3,10 @@ import { hostname } from 'os'
 import buildInfo from '@/generated/build-info.json'
 import { getRedisClient, isRedisAvailable } from '@/lib/redis'
 
+// Force dynamic evaluation - this route must not be statically cached
+// because it reads runtime environment variables and system state
+export const dynamic = 'force-dynamic'
+
 export async function GET() {
   const redis = getRedisClient()
 

apps/web/src/lib/redis.ts

@@ -21,13 +21,21 @@ let redisInitialized = false
  * Returns null if REDIS_URL is not set in environment.
  */
 export function getRedisClient(): Redis | null {
-  if (redisInitialized) {
+  const redisUrl = process.env.REDIS_URL
+
+  // If we've already initialized with a client, return it
+  if (redisInitialized && redisClient) {
     return redisClient
   }
 
+  // If we initialized but got null AND REDIS_URL is still not set, return null
+  // But if REDIS_URL is NOW set (e.g., build-time vs runtime), try again
+  if (redisInitialized && !redisUrl) {
+    return null
+  }
+
   redisInitialized = true
 
-  const redisUrl = process.env.REDIS_URL
   if (!redisUrl) {
     console.log('[Redis] REDIS_URL not set, using in-memory storage')
     return null