feat(infra): remove Go dashboard, dashboard is now part of hub Next.js app

- Remove dashboard container from observability.yml
- Remove infra/docker/dashboard.Dockerfile
- Remove dashboard route from Traefik apps.yaml
- Mount Docker socket on hub container for /api/dashboard
- Remove dashboard build from CI/CD (docker-build-push.yml)
- Update submodule pointer to hub with Next.js dashboard rewrite

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

infra/traefik/dynamic/apps.yaml

@@ -20,16 +20,6 @@ http:
         - common-chain@file
       service: scraper-service
 
-    # ── Dashboard ──
-    dashboard:
-      rule: 'Host(`dashboard.asepharyana.my.id`) || Host(`status.asepharyana.my.id`) || Host(`dashboard.asepharyana.web.id`) || Host(`status.asepharyana.web.id`)'
-      entryPoints:
-        - websecure
-      tls: {}
-      middlewares:
-        - common-chain@file
-      service: dashboard-service
-
     # ── Jaeger UI ──
     jaeger:
       rule: 'Host(`jaeger.asepharyana.my.id`) || Host(`jaeger.asepharyana.web.id`)'
@@ -51,11 +41,6 @@ http:
         servers:
           - url: 'http://scraper-api:4091'
 
-    dashboard-service:
-      loadBalancer:
-        servers:
-          - url: 'http://dashboard:8080'
-
     jaeger-service:
       loadBalancer:
         servers: