Say env var changes take effect at the next deploy or rollback (closes #255)

The hint under the app page's environment variable editor asked for a
container restart. Environment variables are set when a container is
created, and upaas's restart stops and starts the same container, so it
keeps the old values; deploy and rollback each create a new container.
The hint now says so in one sentence, styled with badge-warning, the
warning style the page already uses: its old text-amber-600 class is not
in the built stylesheet. A handler test renders the app page and checks
the hint.

Model: opus-5-5

TODO.md

@@ -20,6 +20,11 @@ regress.
 
 # Completed Steps
 
+- 2026-10-01: The hint under the app page's environment variable editor now says
+  changes take effect at the next deploy or rollback, in the page's warning
+  style, instead of asking for a container restart, which keeps the old values
+  (#255).
+
 - 2026-10-01: An app's first deploy no longer fails when a volume's host path
   does not exist yet: upaas asks Docker to create a missing host path when the
   app's container starts and to leave an existing one alone, so nobody has to

internal/handlers/app_page_env_var_hint_test.go

@@ -0,0 +1,38 @@
+package handlers_test
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"sneak.berlin/go/upaas/internal/service/app"
+)
+
+// TestAppPageEnvVarHint checks that the environment variable editor says
+// changes take effect at the next deploy or rollback, in the warning style.
+func TestAppPageEnvVarHint(t *testing.T) {
+	t.Parallel()
+
+	testCtx := setupTestHandlers(t)
+
+	createdApp, err := testCtx.appSvc.CreateApp(t.Context(), app.CreateAppInput{
+		Name:    "env-hint-app",
+		RepoURL: "git@example.com:user/env-hint-app.git",
+	})
+	require.NoError(t, err)
+
+	request := httptest.NewRequestWithContext(
+		t.Context(), http.MethodGet, "/apps/"+createdApp.ID, nil,
+	)
+	request = addChiURLParams(request, map[string]string{"id": createdApp.ID})
+	recorder := httptest.NewRecorder()
+
+	testCtx.handlers.HandleAppDetail().ServeHTTP(recorder, request)
+
+	require.Equal(t, http.StatusOK, recorder.Code)
+	assert.Contains(t, recorder.Body.String(),
+		`<p class="badge-warning mt-1">Environment variable changes take effect at the next deploy or rollback.</p>`)
+}

templates/app_detail.html

@@ -178,7 +178,7 @@
                                     <button type="submit" class="btn-primary text-sm">Save</button>
                                     <button type="button" @click="editIdx = -1" class="text-gray-500 hover:text-gray-700 text-sm">Cancel</button>
                                 </form>
-                                <p class="text-xs text-amber-600 mt-1">⚠ Container restart needed after env var changes.</p>
+                                <p class="badge-warning mt-1">Environment variable changes take effect at the next deploy or rollback.</p>
                             </td>
                         </template>
                     </tr>