fix: pin better-auth 1.6.23, drop stale CLI, programmatic migrations, fix CI

- Explicitly track latest core (1.6.23); the @better-auth/cli lags at 1.4.21 and
  pulled a second core copy — replaced with a getMigrations() script on the same
  version (src/migrate.ts).
- CI build job matches the proven pattern (no setup-buildx; plain build/push).

.gitea/workflows/build.yaml

@@ -19,18 +19,17 @@ jobs:
   build:
     needs: test
     runs-on: ubuntu-latest
-    container:
-      image: catthehacker/ubuntu:act-latest
+    timeout-minutes: 20
     env:
       IMAGE: git.farh.net/farhoodlabs/intervalsicu-mcp-auth
+      DOCKER_BUILDKIT: "1"
     steps:
       - uses: actions/checkout@v4
-      - name: Set up Docker
-        uses: docker/setup-buildx-action@v3
-      - name: Log in to registry
+      - name: Login to registry
         run: echo "${{ secrets.REGISTRY_TOKEN }}" | docker login git.farh.net -u cpfarhood --password-stdin
-      - name: Build and push
+      - name: Build image
+        run: docker build --progress=plain -t "${IMAGE}:latest" -t "${IMAGE}:${GITHUB_SHA}" .
+      - name: Push image
         run: |
-          docker build -t "$IMAGE:${GITHUB_SHA}" -t "$IMAGE:latest" .
-          docker push "$IMAGE:${GITHUB_SHA}"
-          docker push "$IMAGE:latest"
+          docker push "${IMAGE}:latest"
+          docker push "${IMAGE}:${GITHUB_SHA}"