chore: use DEPOT_TOKEN secret (#10237)

# Which Problems Are Solved

Action runs on PRs from forks can't authenticate at depot.

# How the Problems Are Solved

- The GitHub secret DEPOT_TOKEN is statically passed as env variable to
the steps that use the depot CLI, as described
[here](https://github.com/depot/setup-action#authentication).
- Removed the oidc argument from the depot/setup-action, as we pass the
env statically to the relevant steps.
- The `id-token: write` permission is removed from all workflows, as
it's not needed anymore.

# Additional Changes

Removed the obsolete comment
```yaml
# latest if branch is main, otherwise image version which is the pull request number
```

# Additional Context

Required by these approved PRs so their checks can be executed:
- https://github.com/zitadel/zitadel/pull/9982
- https://github.com/zitadel/zitadel/pull/9958

.github/workflows/login-container.yml

@@ -14,6 +14,9 @@ on:
       login_build_image:
           description: 'The full image tag of the standalone login image'
           value: '${{ inputs.login_build_image_name }}:${{ github.sha }}'
+    secrets:
+      DEPOT_TOKEN:
+        required: true
 
 permissions:
   packages: write
@@ -29,13 +32,10 @@ jobs:
     name: Build Login Container
     runs-on: depot-ubuntu-22.04-8
     permissions:
-      id-token: write
       packages: write
     steps:
       - uses: actions/checkout@v4
       - uses: depot/setup-action@v1
-        with:
-          oidc: true
       - name: Login meta
         id: login-meta
         uses: docker/metadata-action@v5
@@ -55,6 +55,7 @@ jobs:
       - name: Bake login multi-arch
         uses: depot/bake-action@v1
         env:
+          DEPOT_TOKEN: ${{ secrets.DEPOT_TOKEN }}
           NODE_VERSION: ${{ inputs.node_version }}
         with:
           push: true