feat: enhance mobile responsiveness with collapsible controls and automation/effects bars

Added comprehensive mobile support for Phase 15 (Polish & Optimization):

**Mobile Layout Enhancements:**
- Track controls now collapsible on mobile with two states:
  - Collapsed: minimal controls with expand chevron, R/M/S buttons, horizontal level meter
  - Expanded: full height fader, pan control, all buttons
- Track collapse buttons added to mobile view (left chevron for track collapse, right chevron for control collapse)
- Master controls collapse button hidden on desktop (lg:hidden)
- Automation and effects bars now available on mobile layout
- Both bars collapsible with eye/eye-off icons, horizontally scrollable when zoomed
- Mobile vertical stacking: controls → waveform → automation → effects per track

**Bug Fixes:**
- Fixed track controls and waveform container height matching on desktop
- Fixed Modal component prop: isOpen → open in all dialog components
- Fixed TypeScript null check for audioBuffer.duration
- Fixed keyboard shortcut category: 'help' → 'view'

**Technical Improvements:**
- Consistent height calculation using trackHeight variable
- Proper responsive breakpoints with Tailwind (sm:640px, lg:1024px)
- Progressive disclosure pattern for mobile controls

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

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

components/dialogs/MemoryWarningDialog.tsx

@@ -0,0 +1,101 @@
+'use client';
+
+import * as React from 'react';
+import { AlertTriangle, Info, X } from 'lucide-react';
+import { Modal } from '@/components/ui/Modal';
+import { Button } from '@/components/ui/Button';
+import { formatMemorySize } from '@/lib/utils/memory-limits';
+
+interface MemoryWarningDialogProps {
+  open: boolean;
+  estimatedMemoryMB: number;
+  availableMemoryMB?: number;
+  warning: string;
+  fileName?: string;
+  onContinue: () => void;
+  onCancel: () => void;
+}
+
+export function MemoryWarningDialog({
+  open,
+  estimatedMemoryMB,
+  availableMemoryMB,
+  warning,
+  fileName,
+  onContinue,
+  onCancel,
+}: MemoryWarningDialogProps) {
+  if (!open) return null;
+
+  const estimatedBytes = estimatedMemoryMB * 1024 * 1024;
+  const availableBytes = availableMemoryMB ? availableMemoryMB * 1024 * 1024 : undefined;
+
+  return (
+    <Modal open={open} onClose={onCancel} title="">
+      <div className="p-6 max-w-md">
+        {/* Header */}
+        <div className="flex items-start justify-between mb-4">
+          <div className="flex items-center gap-2">
+            <AlertTriangle className="h-5 w-5 text-yellow-500" />
+            <h2 className="text-lg font-semibold">Memory Warning</h2>
+          </div>
+          <button onClick={onCancel} className="text-muted-foreground hover:text-foreground">
+            <X className="h-4 w-4" />
+          </button>
+        </div>
+
+        <p className="text-sm text-muted-foreground mb-4">
+          {warning}
+        </p>
+
+        <div className="space-y-4">
+          {/* File Info */}
+          {fileName && (
+            <div className="flex items-center gap-2 text-sm">
+              <Info className="h-4 w-4 text-muted-foreground" />
+              <span className="font-medium">File:</span>
+              <span className="text-muted-foreground truncate">{fileName}</span>
+            </div>
+          )}
+
+          {/* Memory Details */}
+          <div className="bg-muted/50 border border-border rounded-md p-3 space-y-2">
+            <div className="flex justify-between text-sm">
+              <span className="text-muted-foreground">Estimated Memory:</span>
+              <span className="font-medium">{formatMemorySize(estimatedBytes)}</span>
+            </div>
+            {availableBytes && (
+              <div className="flex justify-between text-sm">
+                <span className="text-muted-foreground">Available Memory:</span>
+                <span className="font-medium">{formatMemorySize(availableBytes)}</span>
+              </div>
+            )}
+          </div>
+
+          {/* Warning Message */}
+          <div className="bg-yellow-500/10 border border-yellow-500/20 rounded-md p-3">
+            <p className="text-sm text-yellow-700 dark:text-yellow-400">
+              <strong>Note:</strong> Loading large files may cause performance issues or browser crashes,
+              especially on devices with limited memory. Consider:
+            </p>
+            <ul className="mt-2 text-sm text-yellow-700 dark:text-yellow-400 space-y-1 list-disc list-inside">
+              <li>Closing other browser tabs</li>
+              <li>Using a shorter audio file</li>
+              <li>Splitting large files into smaller segments</li>
+            </ul>
+          </div>
+
+          {/* Actions */}
+          <div className="flex justify-end gap-2">
+            <Button onClick={onCancel} variant="outline">
+              Cancel
+            </Button>
+            <Button onClick={onContinue} variant="default">
+              Continue Anyway
+            </Button>
+          </div>
+        </div>
+      </div>
+    </Modal>
+  );
+}