ci: use GitHub App authentication (secrets configured)

Now using iterate-evolve GitHub App for authentication:
- Generates token from APP_ID and APP_PRIVATE_KEY
- PRs and merges will show as iterate-evolve[bot]
- No more Patel230 on PRs!

Author: Patel230

.github/workflows/evolve.yml

@@ -16,9 +16,17 @@ jobs:
     env:
       FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: true
     steps:
+      - name: Generate GitHub App token
+        id: generate-token
+        uses: tibdex/github-app-token@v2
+        with:
+          app_id: ${{ secrets.APP_ID }}
+          private_key: ${{ secrets.APP_PRIVATE_KEY }}
+
       - uses: actions/checkout@v4
         with:
           fetch-depth: 0
+          token: ${{ steps.generate-token.outputs.token }}
 
       - name: Clone iteragent for local replace
         run: |
@@ -42,8 +50,8 @@ jobs:
           OPENCODE_BASE_URL: ${{ secrets.OPENCODE_BASE_URL || 'https://opencode.ai/zen/go/v1' }}
           ITERATE_PROVIDER: opencode
           ITERATE_MODEL: ${{ secrets.ITERATE_MODEL || 'kimi-k2.5' }}
-          GH_TOKEN: ${{ secrets.GH_PAT }}
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GH_TOKEN: ${{ steps.generate-token.outputs.token }}
+          GITHUB_TOKEN: ${{ steps.generate-token.outputs.token }}
           DISCORD_WEBHOOK_URL: ${{ secrets.DISCORD_WEBHOOK_URL }}
         run: |
           bash scripts/evolution/evolve.sh