chore: Disable Dependabot (#946)

Add open-pull-requests-limit: 0 to the Docker, GitHub Actions, and UV update blocks in .github/dependabot.yml. This sets the concurrent open PR limit to zero for those ecosystems, preventing Dependabot from creating pull requests and reducing update noise so updates can be handled manually.

Author: yxtay

.github/dependabot.yml

@@ -7,6 +7,7 @@ updates:
       interval: daily
     commit-message:
       prefix: build(docker)
+    open-pull-requests-limit: 0
     groups:
       docker:
         update-types: [minor, patch]
@@ -17,6 +18,7 @@ updates:
       interval: daily
     commit-message:
       prefix: ci(github-actions)
+    open-pull-requests-limit: 0
     groups:
       github-actions:
         update-types: [minor, patch]
@@ -27,6 +29,7 @@ updates:
       interval: daily
     commit-message:
       prefix: build(uv)
+    open-pull-requests-limit: 0
     groups:
       uv:
         update-types: [minor, patch]