fix(practice): add fallback error message when photo upload is blocked

When canUpload is false but there's no specific remediation available
(e.g., due to a bug in access control), show a generic "Unable to upload
photos" banner instead of silently hiding the upload buttons.

This ensures users see feedback when access is unexpectedly denied,
rather than being confused by missing UI elements.

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/web/src/components/practice/OfflineWorkSection.tsx

@@ -94,7 +94,10 @@ export function OfflineWorkSection({
   // Also only show if user can upload
   const showAddTile = photoCount < 8 && canUpload
   // Show remediation when user can't upload but is a teacher with enrolled student
-  const showRemediation = !canUpload && classroomId && studentId
+  const showTeacherRemediation = !canUpload && classroomId && studentId
+  // Show generic access denied message when canUpload is false for unknown reasons
+  // (catches bugs like parent-child link not being recognized)
+  const showGenericAccessDenied = !canUpload && !classroomId
 
   // Entry prompt state (for teachers who need student to enter classroom)
   const [promptSent, setPromptSent] = useState(false)
@@ -602,7 +605,7 @@ export function OfflineWorkSection({
       </div>
 
       {/* Remediation banner - shown when teacher can't upload because student isn't present */}
-      {showRemediation && (
+      {showTeacherRemediation && (
         <div
           data-element="upload-remediation"
           className={css({
@@ -694,6 +697,42 @@ export function OfflineWorkSection({
         </div>
       )}
 
+      {/* Generic access denied banner - shown when upload is blocked for unknown reasons */}
+      {showGenericAccessDenied && (
+        <div
+          data-element="upload-access-denied"
+          className={css({
+            marginTop: '1rem',
+            padding: '1rem',
+            backgroundColor: isDark ? 'red.900/30' : 'red.50',
+            border: '2px solid',
+            borderColor: isDark ? 'red.700' : 'red.300',
+            borderRadius: '12px',
+          })}
+        >
+          <h4
+            className={css({
+              fontSize: '0.9375rem',
+              fontWeight: '600',
+              color: isDark ? 'red.300' : 'red.700',
+              marginBottom: '0.5rem',
+            })}
+          >
+            Unable to upload photos
+          </h4>
+          <p
+            className={css({
+              fontSize: '0.875rem',
+              color: isDark ? 'gray.300' : 'gray.600',
+              lineHeight: '1.5',
+            })}
+          >
+            Your account doesn&apos;t have permission to upload photos for this student. If you
+            believe this is an error, try refreshing the page or logging out and back in.
+          </p>
+        </div>
+      )}
+
       {/* Parsing hint footer - only show if no parsed results yet */}
       {onParse && parsedAttachments.length === 0 && (
         <div