feat: Replace browser alerts with terminal-aesthetic notifications

Replaced all native browser dialogs with custom terminal-style UI:

**Utility Functions** (dashboard.js):
- showConfirmModal() - Reusable confirmation modal with type-based colors
- showInputModal() - Text input modal for user prompts
- Both support keyboard shortcuts (ESC to cancel, Enter to submit)

**Alert Replacements** (22 instances):
- Validation warnings → toast.warning() (amber, 2s)
- Error messages → toast.error() (red, 5s)
- Success messages → toast.success() or toast.warning() with details
- Example: "Bulk close: 5 succeeded, 2 failed" vs simple "Operation complete"

**Confirm Replacements** (3 instances):
- dashboard.js:509 - Bulk close confirmation → showConfirmModal()
- ticket.js:417 - Status change warning → showConfirmModal()
- advanced-search.js:321 - Delete filter → showConfirmModal('error' type)

**Prompt Replacement** (1 instance):
- advanced-search.js:151 - Save filter name → showInputModal()

**Benefits**:
✓ Visual consistency - matches terminal CRT aesthetic
✓ Non-blocking - toasts don't interrupt workflow
✓ Better UX - different colors for different message types
✓ Keyboard friendly - ESC/Enter support in modals
✓ Reusable - modal functions available for future use

All dialogs maintain retro aesthetic with:
- ASCII borders (╚ ╝)
- Terminal green glow
- Monospace fonts
- Color-coded by type (amber warning, red error, cyan info)

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

assets/js/ticket.js

@@ -414,14 +414,27 @@ function updateTicketStatus() {
 
     // Warn if comment is required
     if (requiresComment) {
-        const proceed = confirm(`This status change requires a comment. Please add a comment explaining the reason for this transition.\n\nProceed with status change to "${newStatus}"?`);
-        if (!proceed) {
-            // Reset to current status
-            statusSelect.selectedIndex = 0;
-            return;
-        }
+        showConfirmModal(
+            'Status Change Requires Comment',
+            `This transition to "${newStatus}" requires a comment explaining the reason.\n\nPlease add a comment before changing the status.`,
+            'warning',
+            () => {
+                // User confirmed, proceed with status change
+                performStatusChange(statusSelect, newStatus);
+            },
+            () => {
+                // User cancelled, reset to current status
+                statusSelect.selectedIndex = 0;
+            }
+        );
+        return;
     }
 
+    performStatusChange(statusSelect, newStatus);
+});
+
+// Extract status change logic into reusable function
+function performStatusChange(statusSelect, newStatus) {
     // Extract ticket ID
     let ticketId;
     if (window.location.href.includes('?id=')) {