fix: add github_token to claude-code-action workflows (#1577)

The claude-code-action workflows were failing due to OIDC token
exchange issues. The action attempts to authenticate automatically
using OIDC, but when this fails it requires an explicit github_token.

This commit adds the github_token parameter using secrets.GITHUB_TOKEN
to both pr-assignment-check.yml and pr-stale-check.yml workflows.

Fixes the "Invalid OIDC token" error:
https://github.com/lingodotdev/lingo.dev/actions/runs/19286588549

Author: maxprilutskiy

.github/workflows/pr-assignment-check.yml

@@ -22,6 +22,7 @@ jobs:
       - uses: anthropics/claude-code-action@v1
         with:
           anthropic_api_key: ${{ secrets.CLAUDE_CODE_API_KEY }}
+          github_token: ${{ secrets.GITHUB_TOKEN }}
           prompt: |
             EXEMPT USERS: @maxprilutskiy, @vrcprl, @davidturnbull, @monicabe, @sumitsaurabh927, @AleksandrSl (skip all checks if PR author is one of these)
 

.github/workflows/pr-stale-check.yml

@@ -17,6 +17,7 @@ jobs:
       - uses: anthropics/claude-code-action@v1
         with:
           anthropic_api_key: ${{ secrets.CLAUDE_CODE_API_KEY }}
+          github_token: ${{ secrets.GITHUB_TOKEN }}
           prompt: |
             EXEMPT USERS: @maxprilutskiy, @vrcprl, @davidturnbull, @monicabe, @sumitsaurabh927, @AleksandrSl