Add CODEOWNERS and dependabot.yml for security compliance (#928)

- Add CODEOWNERS file with team ownership (@davidliu @MaxHeimbrock @xianshijing-lk)
- Add dependabot.yml for automated security updates (gradle, github-actions)
- Configure versioning-strategy to only update for security fixes

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: xianshijing-lk

.github/CODEOWNERS

@@ -0,0 +1,4 @@
+# CODEOWNERS for client-sdk-android
+# These owners will be requested for review on all PRs
+
+* @davidliu @MaxHeimbrock @xianshijing-lk

.github/dependabot.yml

@@ -0,0 +1,14 @@
+version: 2
+updates:
+  - package-ecosystem: "gradle"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    open-pull-requests-limit: 10
+    versioning-strategy: "increase-if-necessary"
+
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    open-pull-requests-limit: 5