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

.golangci.yml

@@ -0,0 +1,14 @@
+version: "2"
+
+linters:
+  default: none
+  enable:
+    - errcheck
+    - govet
+    - staticcheck
+    - unused
+  exclusions:
+    paths:
+      - web/ui
+      - electron
+      - third_party/akaiutil/