chore(deps): use uv ecosystem for dependabot python updates (#12309)

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

.github/dependabot.yml

@@ -11,8 +11,8 @@ updates:
       - "jmelahman"
     labels:
       - "dependabot:actions"
-  - package-ecosystem: "pip"
-    directory: "/backend"
+  - package-ecosystem: "uv"
+    directory: "/"
     schedule:
       interval: "weekly"
     cooldown: