ci: add CODEOWNERS + auto-assign (codejanovic)

Reviewer via CODEOWNERS, Assignee via auto-assign workflow.
Standard: personal vault/concepts/github-workflow-standard.md

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

Author: glaudeee

.github/CODEOWNERS

@@ -0,0 +1,3 @@
+# Code owner: auto-request review from codejanovic on every PR.
+# Enforce via branch protection "Require review from Code Owners".
+* @codejanovic

.github/workflows/auto-assign.yml

@@ -0,0 +1,24 @@
+# Sets codejanovic as ASSIGNEE on every PR (reviewer handled by .github/CODEOWNERS).
+name: Auto-assign
+
+on:
+  pull_request:
+    types: [opened, reopened]
+
+permissions:
+  pull-requests: write
+
+jobs:
+  assign:
+    if: github.event.pull_request.head.repo.full_name == github.repository
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/github-script@v7
+        with:
+          script: |
+            await github.rest.issues.addAssignees({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: context.issue.number,
+              assignees: ['codejanovic'],
+            });