feat: single-step app creation with auto-slug, JAR upload, and deploy

Replace inline create form with a modal that handles the full flow:
- Name → auto-computed slug (editable if needed)
- Environment picker
- JAR file upload
- "Deploy immediately" toggle (on by default)
- Single "Create & Deploy" button runs all three API calls sequentially
  with step indicator

After creation, navigates directly to the new app's detail view.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/pages/AppsTab/AppsTab.module.css

@@ -10,20 +10,63 @@
   margin-bottom: 12px;
 }
 
-.createForm {
+/* Create modal */
+.createModal {
+  display: flex;
+  flex-direction: column;
+  gap: 14px;
+}
+
+.createField {
+  display: flex;
+  flex-direction: column;
+  gap: 4px;
+}
+
+.createLabel {
+  font-size: 12px;
+  font-weight: 500;
+  color: var(--text-muted);
+}
+
+.createLabelHint {
+  font-weight: 400;
+  font-style: italic;
+  margin-left: 6px;
+}
+
+.fileRow {
   display: flex;
   align-items: center;
-  gap: 8px;
-  padding: 12px;
-  margin-bottom: 12px;
-  border: 1px solid var(--border-subtle);
-  border-radius: 6px;
-  background: var(--bg-raised);
+  gap: 10px;
+}
+
+.fileName {
+  font-size: 12px;
+  color: var(--text-primary);
+  font-family: var(--font-mono);
+}
+
+.deployToggle {
+  display: flex;
+  align-items: center;
+  gap: 10px;
+  font-size: 12px;
+  color: var(--text-primary);
+}
+
+.stepIndicator {
+  font-size: 12px;
+  color: var(--accent, #6c7aff);
+  font-style: italic;
 }
 
 .createActions {
   display: flex;
   gap: 8px;
+  justify-content: flex-end;
+  padding-top: 8px;
+  border-top: 1px solid var(--border-subtle);
 }
 
 .nativeSelect {