ci: make Dependabot use conventional commit PR titles (#773)

Adds commit-message.prefix to each ecosystem so Dependabot's PR
titles pass the conventional-pr-title check:
- uv -> "chore(deps): ..."
- github-actions -> "ci(deps): ..."

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: dbrattli

.github/dependabot.yml

@@ -5,6 +5,10 @@ updates:
     schedule:
       interval: "weekly"
     open-pull-requests-limit: 10
+    commit-message:
+      prefix: "chore"
+      prefix-development: "chore"
+      include: "scope"
     groups:
       python-dependencies:
         patterns:
@@ -15,6 +19,9 @@ updates:
     schedule:
       interval: "weekly"
     open-pull-requests-limit: 5
+    commit-message:
+      prefix: "ci"
+      include: "scope"
     groups:
       github-actions:
         patterns: