fix: resolve ESLint errors and warnings

- Add emoji accessibility labels (jsx-a11y/accessible-emoji)
- Remove unused imports and variables
- Fix async functions without await
- Add dev directory to ESLint ignore list
- Add eslint-disable comment for necessary console.error
- Clean up unused route file

All ESLint errors resolved (0 errors, 33 warnings remaining)

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

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

src/collections/invoices.ts

@@ -1,4 +1,4 @@
-import {
+import type {
   AccessArgs,
   CollectionAfterChangeHook,
   CollectionBeforeChangeHook,
@@ -390,7 +390,7 @@ export function createInvoicesCollection(pluginConfig: BillingPluginConfig): Col
       ] satisfies CollectionBeforeChangeHook<Invoice>[],
       beforeValidate: [
         ({ data }) => {
-          if (!data) return
+          if (!data) {return}
 
           // If using extractor, customer relationship is required
           if (customerRelationSlug && customerInfoExtractor && !data.customer) {