fix: enable Service Worker registration in dev mode for testing

With devOptions.enabled: true, vite-plugin-pwa should serve the SW
in dev mode. Now we:
1. Attempt registration in both dev and prod
2. In dev mode, check if SW file exists and has correct MIME type first
3. Only register if file is actually available (not HTML fallback)
4. Handle errors gracefully with informative warnings

This allows testing image caching in dev mode when vite-plugin-pwa
is properly serving the Service Worker file.

src/main.tsx

@@ -7,14 +7,14 @@ import 'react-loading-skeleton/dist/skeleton.css'
 
 // Register Service Worker for PWA functionality
 // With injectRegister: null, we need to register manually
-// Note: With injectManifest strategy, SW file is only built in production
-// So we skip registration in dev mode (image caching won't work in dev, but that's okay)
-if ('serviceWorker' in navigator && import.meta.env.PROD) {
+// With devOptions.enabled: true, vite-plugin-pwa serves SW in dev mode too
+if ('serviceWorker' in navigator) {
   window.addEventListener('load', () => {
     const swPath = '/sw.js'
     
     console.log('[sw-registration] Attempting to register Service Worker:', swPath, {
       isProd: import.meta.env.PROD,
+      isDev: import.meta.env.DEV,
       hasController: !!navigator.serviceWorker.controller
     })
     
@@ -38,9 +38,42 @@ if ('serviceWorker' in navigator && import.meta.env.PROD) {
         return existingReg
       }
       
-      // Not registered yet, try to register (production only)
+      // Not registered yet, try to register
+      // In dev mode, check if SW file exists and has correct MIME type before registering
+      if (import.meta.env.DEV) {
+        try {
+          const response = await fetch(swPath)
+          const contentType = response.headers.get('content-type') || ''
+          const isJavaScript = contentType.includes('javascript') || contentType.includes('application/javascript')
+          
+          console.log('[sw-registration] Dev mode - checking SW file:', {
+            status: response.status,
+            contentType,
+            isJavaScript,
+            isHTML: contentType.includes('text/html')
+          })
+          
+          if (response.ok && isJavaScript) {
+            console.log('[sw-registration] Service Worker file available in dev mode, proceeding with registration')
+            return await navigator.serviceWorker.register(swPath)
+          } else {
+            console.warn('[sw-registration] ⚠️ Service Worker file not available in dev mode:', {
+              status: response.status,
+              contentType
+            })
+            console.warn('[sw-registration] Image caching will not work in dev mode - test in production build')
+            return null
+          }
+        } catch (err) {
+          console.warn('[sw-registration] ⚠️ Could not check Service Worker file in dev mode:', err)
+          console.warn('[sw-registration] Image caching will not work in dev mode - test in production build')
+          return null
+        }
+      } else {
+        // In production, just register directly
         console.log('[sw-registration] No existing registration, attempting to register:', swPath)
         return await navigator.serviceWorker.register(swPath)
+      }
     })
       .then(registration => {
         if (!registration) return
@@ -99,11 +132,14 @@ if ('serviceWorker' in navigator && import.meta.env.PROD) {
           name: error.name,
           stack: error.stack
         })
+        
+        // In dev mode, this is expected if vite-plugin-pwa isn't serving the SW
+        if (import.meta.env.DEV) {
+          console.warn('[sw-registration] ⚠️ This is expected in dev mode if vite-plugin-pwa is not serving the SW file')
+          console.warn('[sw-registration] Image caching will not work in dev mode - test in production build')
+        }
       })
   })
-} else if (import.meta.env.DEV) {
-  // In dev mode, SW registration is skipped (injectManifest requires build)
-  console.log('[sw-registration] Skipping Service Worker registration in dev mode (injectManifest requires build)')
 } else {
   console.warn('[sw-registration] ⚠️ Service Workers not supported in this browser')
 }