feat: swap Redis for Dragonfly, fix remote installs, self-hosted email-only auth

- Replace redis:7-alpine with Dragonfly (Redis-protocol compatible; go-redis
  client unchanged) in root, infra, and backend-dev compose files. Bounded
  defaults --proactor_threads/--maxmemory so it boots on small VPSs.
- Frontend now defaults to same-origin API calls; nginx proxies /api/* to the
  backend (WebSocket-aware, docker DNS resolver for upstream re-resolution).
  Removes the baked localhost:8082 that broke installs reached by IP/domain.
- /auth/bootstrap returns configured OAuth providers; the UI hides
  GitHub/Google buttons unless real credentials exist. Self-hosted stays
  email/password only - OAuth reserved for a future managed offering.
- Sidecar ignores PLACEHOLDER_* OAuth credentials and trusts same-host
  origins dynamically (Origin host == request Host) so remote installs pass
  origin checks without config; cross-origin requests still rejected.
- install.sh writes ENVIRONMENT=production; COOKIE_SECURE=false in
  production is now a startup warning instead of fatal (plain-HTTP installs).
- Bootstrap failure surfaces an error notice instead of silently rendering
  the sign-in page.

Authored By: TDvorak <[email protected]>

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

infra/docker-compose.yml

@@ -65,12 +65,16 @@ services:
       timeout: 10s
       retries: 3
 
-  redis:
-    image: redis:7-alpine
-    container_name: containr-redis
-    command: redis-server --requirepass ${REDIS_PASSWORD:-dev_redis_123}
+  dragonfly:
+    image: docker.dragonflydb.io/dragonflydb/dragonfly:${DRAGONFLY_VERSION:-latest}
+    container_name: containr-dragonfly
+    command:
+      - --requirepass=${REDIS_PASSWORD:-dev_redis_123}
+      - --proactor_threads=${DRAGONFLY_THREADS:-1}
+      - --maxmemory=${DRAGONFLY_MAXMEMORY:-256mb}
+      - --dir=/data
     volumes:
-      - redis_data:/data
+      - dragonfly_data:/data
     networks:
       - containr-network
     restart: unless-stopped
@@ -89,7 +93,7 @@ services:
       - "8082:8080"
     environment:
       - DATABASE_URL=postgres://${POSTGRES_USER:-containr_user}:${POSTGRES_PASSWORD:-dev_password_123}@postgres:5432/${POSTGRES_DB:-containr}?sslmode=disable
-      - REDIS_URL=redis://:${REDIS_PASSWORD:-dev_redis_123}@redis:6379/0
+      - REDIS_URL=redis://:${REDIS_PASSWORD:-dev_redis_123}@dragonfly:6379/0
       - PORT=8080
       - HOST=0.0.0.0
       - ENVIRONMENT=${ENVIRONMENT:-production}
@@ -135,7 +139,7 @@ services:
     depends_on:
       postgres:
         condition: service_healthy
-      redis:
+      dragonfly:
         condition: service_healthy
     restart: unless-stopped
     healthcheck:
@@ -160,8 +164,8 @@ services:
       context: ../app/frontend
       dockerfile: Dockerfile
       args:
-        VITE_API_URL: ${VITE_API_URL:-http://localhost:8082}
-        VITE_AUTH_URL: ${VITE_AUTH_URL:-http://localhost:8082/api/auth}
+        VITE_API_URL: ${VITE_API_URL:-}
+        VITE_AUTH_URL: ${VITE_AUTH_URL:-}
     container_name: containr-frontend
     ports:
       - "3000:80"
@@ -203,7 +207,7 @@ services:
 volumes:
   postgres_data:
     driver: local
-  redis_data:
+  dragonfly_data:
     driver: local
 
 networks: