chore: standardize Dependabot with grouping and labels

Add grouped PRs (actions grouped by pattern, pip/npm/docker by update-type).
Monday schedule, conventional commit prefixes, dependency labels.

Author: bakerboy448

.github/dependabot.yml

@@ -1,8 +1,17 @@
+---
 version: 2
 updates:
   - package-ecosystem: github-actions
     directory: /
     schedule:
       interval: weekly
+      day: monday
     commit-message:
       prefix: "ci"
+    groups:
+      github-actions:
+        patterns:
+          - "*"
+    labels:
+      - dependencies
+      - github-actions