Fix upload stuck pending: validate blob readability before upload

iOS Safari can evict blob data from IndexedDB while keeping the Blob
reference intact (instanceof/size checks pass but actual data read
fails). This caused upload POST to throw 'Load failed' client-side,
never reaching the server, burning retries endlessly.

Changes:
- Add validateBlobReadable() that reads first byte to verify data access
- If blob is unreadable, mark as 'failed' immediately with clear message
- Re-read photo from IndexedDB before upload for fresh blob reference
- Capture detailed error name/type in catch for better diagnostics
- Bump SW cache versions to v14/v10 to force new code delivery

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/static/js/sync.js

@@ -129,15 +129,39 @@ const Sync = {
         const retryCount = photo.retryCount || 0;
 
         try {
+            // Re-read photo from IndexedDB to get a fresh blob reference
+            // (iOS Safari can invalidate blob references between reads)
+            const freshPhoto = await Storage.db.photos.get(photo.id);
+            if (!freshPhoto || (freshPhoto.status !== 'pending' && freshPhoto.status !== 'uploading')) {
+                console.log('[SYNC] Photo no longer pending, skipping:', photo.id);
+                return true;
+            }
+
+            const blob = freshPhoto.blob;
+
             console.log('[SYNC] Uploading:', photo.filename,
-                '(' + (photo.blob ? (photo.blob.size / 1024 / 1024).toFixed(1) + 'MB' : 'no blob') + ')',
+                '(' + (blob ? (blob.size / 1024 / 1024).toFixed(1) + 'MB' : 'no blob') + ')',
                 'attempt', retryCount + 1, 'of', this.MAX_RETRIES);
 
-            // Validate blob before attempting upload
-            if (!photo.blob || !(photo.blob instanceof Blob) || photo.blob.size === 0) {
+            // Validate blob reference exists
+            if (!blob || !(blob instanceof Blob) || blob.size === 0) {
                 throw new Error('Photo data is missing or corrupted - please delete and re-capture');
             }
 
+            // Actually try to read the blob to verify data is accessible
+            // (iOS Safari can evict blob data from IndexedDB while keeping the reference)
+            const readable = await this.validateBlobReadable(blob);
+            if (!readable) {
+                // Blob data is gone — no amount of retrying will fix this
+                console.error('[SYNC] Blob data is no longer readable:', photo.filename);
+                await Storage.updatePhoto(photo.id, {
+                    status: 'failed',
+                    lastError: 'Photo data was lost by the browser - please re-capture',
+                    error: 'Photo data was lost by the browser - please re-capture'
+                });
+                return false;
+            }
+
             await Storage.updatePhoto(photo.id, { status: 'uploading' });
 
             // Prevent page navigation during upload
@@ -162,10 +186,8 @@ const Sync = {
                 }
             }
 
-            const uploadBlob = photo.blob;
-
             const formData = new FormData();
-            formData.append('file', uploadBlob, photo.filename);
+            formData.append('file', blob, photo.filename);
 
             const uploadUrl = '/api/files/upload?path=' + encodeURIComponent(photo.targetPath);
 
@@ -185,7 +207,10 @@ const Sync = {
                 if (fetchErr.name === 'AbortError') {
                     throw new Error('Upload timed out (' + (this.UPLOAD_TIMEOUT_MS / 1000) + 's)');
                 }
-                throw fetchErr;
+                // Capture detailed error info for debugging
+                const errDetail = fetchErr.name + ': ' + fetchErr.message;
+                console.error('[SYNC] Fetch threw:', errDetail);
+                throw new Error('Network error: ' + errDetail);
             }
             clearTimeout(timeoutId);
 
@@ -241,12 +266,13 @@ const Sync = {
 
         } catch (error) {
             this._setUploading(false);
-            console.error('[SYNC] Upload failed:', error.message, '(attempt', retryCount + 1 + ')');
+            const errMsg = (error.name || 'Error') + ': ' + error.message;
+            console.error('[SYNC] Upload failed:', errMsg, '(attempt', retryCount + 1 + ')');
             await Storage.updatePhoto(photo.id, {
                 status: 'pending',
                 retryCount: retryCount + 1,
-                lastError: error.message,
-                error: error.message
+                lastError: errMsg,
+                error: errMsg
             });
             return false;
         }
@@ -268,6 +294,19 @@ const Sync = {
         }
     },
 
+    async validateBlobReadable(blob) {
+        try {
+            // Try to read the first byte — if iOS has evicted the data,
+            // this will throw even though the Blob reference looks valid
+            const slice = blob.slice(0, 1);
+            const buf = await slice.arrayBuffer();
+            return buf.byteLength > 0;
+        } catch (e) {
+            console.error('[SYNC] Blob readability check failed:', e.message);
+            return false;
+        }
+    },
+
     async checkFileExists(path) {
         try {
             const verifyUrl = '/api/files/verify?path=' + encodeURIComponent(path);

app/static/sw.js

@@ -1,9 +1,9 @@
 // NextSnap Service Worker
 // Provides offline-first caching for the app shell
 
-const CACHE_VERSION = 'nextsnap-v13';
-const APP_SHELL_CACHE = 'nextsnap-shell-v9';
-const RUNTIME_CACHE = 'nextsnap-runtime-v9';
+const CACHE_VERSION = 'nextsnap-v14';
+const APP_SHELL_CACHE = 'nextsnap-shell-v10';
+const RUNTIME_CACHE = 'nextsnap-runtime-v10';
 
 // Assets to cache on install
 const APP_SHELL_ASSETS = [