fix: Improve Assigned To column sorting behavior

Fixed sorting logic for the "Assigned To" column on dashboard:

Problem:
- "Unassigned" was sorted alphabetically with user names
- Appeared randomly in middle of list (after 'S', before 'V')
- Made it hard to find unassigned tickets when sorted

Solution:
- "Unassigned" tickets now always appear at end of list
- Regardless of sort direction (A→Z or Z→A)
- Assigned user names still sort normally among themselves
- Example A→Z: Alice, Bob, Charlie... Unassigned
- Example Z→A: Zack, Yolanda, Xavier... Unassigned

This keeps unassigned tickets grouped together and predictable.

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

assets/js/dashboard.js

@@ -141,6 +141,24 @@ function sortTable(table, column) {
             return currentDirection === 'asc' ? dateA - dateB : dateB - dateA;
         }
 
+        // Special handling for "Assigned To" column
+        if (headerText === 'assigned to') {
+            const aUnassigned = aValue === 'Unassigned';
+            const bUnassigned = bValue === 'Unassigned';
+
+            // Both unassigned - equal
+            if (aUnassigned && bUnassigned) return 0;
+
+            // Put unassigned at the end regardless of sort direction
+            if (aUnassigned) return 1;
+            if (bUnassigned) return -1;
+
+            // Otherwise sort names normally
+            return currentDirection === 'asc'
+                ? aValue.localeCompare(bValue)
+                : bValue.localeCompare(aValue);
+        }
+
         // Numeric comparison
         const numA = parseFloat(aValue);
         const numB = parseFloat(bValue);