Update build configuration and improve token handling

- Change CI container image to debian:trixie-slim and set GOPROXY.
- Update Go version to 1.26 in Dockerfile and go.mod.
- Refactor token validation to use SHA-256 hashes instead of plain tokens.
- Add network policy to restrict access to the service.
- Enhance README with new configuration details and usage examples.
- Add tests for new token hash validation logic.

.gitea/workflows/build.yaml

@@ -10,11 +10,23 @@ jobs:
   verify:
     runs-on: container-builder
     container:
-      image: golang:1.24-bookworm
+      image: debian:trixie-slim
+    env:
+      GOPROXY: https://gitea.nehmer.net/api/packages/torben/go,https://proxy.golang.org,direct
     steps:
+      - name: Install CI Dependencies
+        run: |
+          apt-get update
+          apt-get install -y --no-install-recommends git nodejs curl unzip ca-certificates
+
       - name: Checkout Code
         uses: actions/checkout@v4
 
+      - name: Setup Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: '1.26.x'
+
       - name: Show Go Version
         run: go version