chore: add JS/ESLint toolchain, refactor onclick to event delegation

- Add ESLint config for web/ui (flat config, golangci-lint-compatible)
- Add js-lint task to mise.toml (npm run lint in web/ui)
- Add ESLint check to check-toolchain.sh
- Add .golangci.yml for golangci-lint v2 with correct exclusions
- Refactor app.js: replace inline onclick with data-action + event delegation
- Add null checks and HTTP status checks to browseWavs
- Add web/ui/node_modules/ to .gitignore

web/ui/package.json

@@ -0,0 +1,11 @@
+{
+  "name": "akai-utils-web-ui",
+  "version": "1.0.0",
+  "description": "Web UI for AKAI Utils",
+  "scripts": {
+    "lint": "eslint *.js"
+  },
+  "devDependencies": {
+    "eslint": "^9.0.0"
+  }
+}