ci: add conventional commit prefixes to dependabot PR titles (#48)

Configure dependabot to use "ci:" prefix for GitHub Actions updates
and "chore:" prefix for pip dependency updates, so PRs pass the
semantic PR title check automatically.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: FBumann

.github/dependabot.yml

@@ -4,6 +4,8 @@ updates:
     directory: "/"
     schedule:
       interval: "weekly"
+    commit-message:
+      prefix: "chore"
     groups:
       dev-dependencies:
         patterns:
@@ -23,3 +25,5 @@ updates:
     directory: "/"
     schedule:
       interval: "weekly"
+    commit-message:
+      prefix: "ci"