ci: rename secret from GITEA_TOKEN to CI_TOKEN

Gitea secrets cannot start with GITEA_ or GITHUB_ prefix.

.gitea/workflows/pr-check.yml

@@ -1,5 +1,8 @@
 name: PR Checks
 
+env:
+  GITEA_TOKEN: ${{ secrets.CI_TOKEN }}
+
 on:
   pull_request:
     branches: [main]

.gitea/workflows/release.yml

@@ -1,5 +1,8 @@
 name: Release & Publish
 
+env:
+  GITEA_TOKEN: ${{ secrets.CI_TOKEN }}
+
 on:
   push:
     branches: [main]
@@ -117,5 +120,5 @@ jobs:
         run: |
           uv publish \
             --username ${{ github.actor }} \
-            --password ${{ secrets.GITEA_TOKEN }} \
+            --password ${{ env.GITEA_TOKEN }} \
             https://git.much-data.ru/api/packages/${{ github.repository_owner }}/pypi