docs: Complete Sprint 1 - Backend health check fixed

✅ Sprint 1 Complete:
- Changed health check from curl to wget (alpine compatible)
- Changed localhost to 127.0.0.1 (fixes DNS issues with Tailscale/Docker)
- Backend now shows (healthy) status
- Added CREDENTIALS.md with login info
- Documented solution in SPRINT-1-HEALTHCHECK.md

Login credentials:
- Email: admin@runfoo.com
- Password: password123
- URL: https://777wolfpack.runfoo.run

docker-compose.yml

@@ -50,7 +50,7 @@ services:
     networks:
       - internal
     healthcheck:
-      test: [ "CMD", "wget", "-q", "-O-", "http://localhost:3000/api/healthz" ]
+      test: [ "CMD", "wget", "-q", "-O-", "http://127.0.0.1:3000/api/healthz" ]
       interval: 30s
       timeout: 10s
       retries: 3

docs/SPRINT-1-HEALTHCHECK.md

@@ -1,7 +1,7 @@
 # Sprint 1: Fix Backend Health Check
 
 **Date**: 2025-12-09  
-**Status**: In Progress  
+**Status**: ✅ Complete  
 **Duration**: 30 minutes  
 **Priority**: 🔴 Critical
 
@@ -42,15 +42,21 @@ However, the backend container (node:20-alpine) **does not have curl installed**
 
 ## ✅ Solution
 
-### Option 1: Use wget (already available in alpine)
+### Final Fix
 
-Change health check to use `wget` instead of `curl`.
+Changed health check to use:
 
-### Option 2: Install curl in Dockerfile
+1. **wget** instead of curl (alpine has wget by default)
+2. **127.0.0.1** instead of localhost (avoids DNS resolution issues in Docker networking)
 
-Add `curl` to the alpine packages.
+```yaml
+healthcheck:
+  test: [ "CMD", "wget", "-q", "-O-", "http://127.0.0.1:3000/api/healthz" ]
+```
 
-**Chosen**: Option 1 (wget) - simpler, no rebuild needed for testing.
+### Why 127.0.0.1 instead of localhost?
+
+In some Docker networking configurations (especially with Tailscale or custom networks), `localhost` DNS resolution can be problematic. Using `127.0.0.1` bypasses DNS entirely and directly uses the loopback interface.
 
 ---
 
@@ -90,10 +96,10 @@ docker compose ps
 
 ## 📊 Success Criteria
 
-- [ ] Backend container shows `(healthy)` status
-- [ ] Health check endpoint returns 200 OK
-- [ ] No errors in backend logs
-- [ ] Application remains accessible at <https://777wolfpack.runfoo.run>
+- [x] Backend container shows `(healthy)` status
+- [x] Health check endpoint returns 200 OK
+- [x] No errors in backend logs
+- [x] Application remains accessible at <https://777wolfpack.runfoo.run>>
 
 ---