ci: switch runs-on to ubuntu-latest to match runner label

The self-hosted Gitea runner advertises itself as `ubuntu-latest`,
not `self-hosted`, so the jobs were never getting picked up.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -12,7 +12,7 @@ permissions:
 jobs:
   lint-and-test:
     name: Lint + build + test
-    runs-on: self-hosted
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
 

.gitea/workflows/e2e.yml

@@ -19,7 +19,7 @@ permissions:
 
 jobs:
   e2e:
-    runs-on: self-hosted
+    runs-on: ubuntu-latest
     timeout-minutes: 45
     steps:
       - uses: actions/checkout@v4

.gitea/workflows/release.yml

@@ -18,7 +18,7 @@ permissions:
 
 jobs:
   release:
-    runs-on: self-hosted
+    runs-on: ubuntu-latest
     timeout-minutes: 45
     steps:
       - uses: actions/checkout@v4