Add category typeahead with autocomplete suggestions

Changed the category input to a typeahead component in both Add Feature and
Edit Feature dialogs. The component suggests existing categories from
features and allows typing new ones. Categories are saved to feature_list.json.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/playwright.config.ts

@@ -1,6 +1,7 @@
 import { defineConfig, devices } from "@playwright/test";
 
 const port = process.env.TEST_PORT || 3007;
+const reuseServer = process.env.TEST_REUSE_SERVER === "true";
 
 export default defineConfig({
   testDir: "./tests",
@@ -21,10 +22,14 @@ export default defineConfig({
       use: { ...devices["Desktop Chrome"] },
     },
   ],
-  webServer: {
-    command: `npx next dev -p ${port}`,
-    url: `http://localhost:${port}`,
-    reuseExistingServer: !process.env.CI,
-    timeout: 120000,
-  },
+  ...(reuseServer
+    ? {}
+    : {
+        webServer: {
+          command: `npx next dev -p ${port}`,
+          url: `http://localhost:${port}`,
+          reuseExistingServer: !process.env.CI,
+          timeout: 120000,
+        },
+      }),
 });