ci(deps): group dependabot updates per ecosystem

Reduce PR noise by combining daily dependabot updates into a single
grouped PR per ecosystem (gomod and github-actions).

Author: claude

.github/dependabot.yml

@@ -4,7 +4,15 @@ updates:
     directory: "/"
     schedule:
       interval: "daily"
+    groups:
+      gomod:
+        patterns:
+          - "*"
   - package-ecosystem: github-actions
     directory: /
     schedule:
       interval: "daily"
+    groups:
+      github-actions:
+        patterns:
+          - "*"