i18n: useCoreCommands.ts has ~80 hardcoded English command label/menubarLabel strings

All command objects in `src/composables/useCoreCommands.ts` have hardcoded English `label` and `menubarLabel` strings. Only `Comfy.Queue.ToggleOverlay` uses `t()`.

### Affected Entries

**File operations:** "New Blank Workflow", "Open Workflow", "Save Workflow", "Save As", "Rename", "Load Default Workflow", "Export", "Export (API)"

**Queue operations:** "Interrupt", "Clear Pending Tasks", "Queue Prompt", "Queue Prompt (Front)"

**View operations:** "Show Settings Dialog" / "Settings", "Reset View", "Clipspace", "Refresh Node Definitions", "Toggle Theme"

**Node operations:** "Group Selected Nodes", "Mute/Unmute Selected Nodes", "Bypass/Unbypass Selected Nodes", "Toggle Selection"

**Canvas operations:** "Canvas Toggle Lock", "Lock Canvas", "Unlock Canvas", "Toggle Snap to Grid", "Zoom In", "Zoom Out", "Zoom to Fit"

**Other:** "Node Shortcuts", "Queue size: " (status bar), plus native `confirm("Clear workflow?")` and `confirm("Load default workflow?")` dialogs (~line 231)

### Suggested Fix

1. Migrate all command label/menubarLabel to i18n keys (add to `src/locales/en/commands.json` or `src/locales/en/main.json`)
2. Replace native `confirm()` with app dialog components using i18n text