gallery upload: better OCR error messages

- Catches 'unknown error' from Tesseract.js (unsupported
  image formats like RAW/DNG) and shows helpful guidance:
  'Use the 📸 live camera instead'
- Falls through to actual error message for other failures
- Better null-safety on error object

static/index.html

@@ -2649,7 +2649,14 @@
             if (ocrEl) ocrEl.innerHTML = '❌ No machine ID detected. <button class="btn btn-outline btn-sm" onclick="document.getElementById(\'scanMachineId\').value=prompt(\'Enter machine ID:\');handleBarcode(document.getElementById(\'scanMachineId\').value)">Enter manually</button>';
           }
         } catch (ocrErr) {
-          if (ocrEl) ocrEl.textContent = '❌ OCR failed: ' + ocrErr.message;
+          if (ocrEl) {
+            const msg = ocrErr.message || '';
+            if (msg.includes('unknown error') || msg === 'Client OCR failed: ') {
+              ocrEl.innerHTML = '❌ Photo format not supported by browser OCR. Use the 📸 live camera instead.';
+            } else {
+              ocrEl.textContent = '❌ OCR failed: ' + msg;
+            }
+          }
         }
 
         // Extract GPS from EXIF
@@ -3445,7 +3452,8 @@
         result = await Promise.race([ocrPromise, timeoutPromise]);
       } catch (e) {
         updateOcrProgress({ status: 'error' });
-        throw new Error('Client OCR failed: ' + (e.message || 'unknown error'));
+        const reason = (e && e.message) ? e.message : (e ? String(e) : 'image format not supported by browser');
+        throw new Error('Client OCR failed: ' + reason);
       }
 
       updateOcrProgress({ status: 'done' });