Rework desktop install / startup UX (#5292)

### Summary

Complete redesign of Desktop app installer, implementing the new app
startup progress system and error reporting.

src/locales/en/main.json

@@ -18,6 +18,7 @@
     "calculatingDimensions": "Calculating dimensions",
     "import": "Import",
     "loadAllFolders": "Load All Folders",
+    "logoAlt": "ComfyUI Logo",
     "refresh": "Refresh",
     "refreshNode": "Refresh Node",
     "terminal": "Terminal",
@@ -406,6 +407,27 @@
     "migration": "Migration",
     "desktopSettings": "Desktop Settings",
     "chooseInstallationLocation": "Choose Installation Location",
+    "gpuPicker": {
+      "title": "Choose your hardware setup",
+      "recommended": "RECOMMENDED",
+      "nvidiaSubtitle": "NVIDIA CUDA",
+      "cpuSubtitle": "CPU Mode",
+      "manualSubtitle": "Manual Setup",
+      "appleMetalDescription": "Leverages your Mac's GPU for faster speed and a better overall experience",
+      "nvidiaDescription": "Use your NVIDIA GPU with CUDA acceleration for the best performance.",
+      "cpuDescription": "Use CPU mode for compatibility when GPU acceleration is not available",
+      "manualDescription": "Configure ComfyUI manually for advanced setups or unsupported hardware"
+    },
+    "locationPicker": {
+      "title": "Choose where to install ComfyUI",
+      "subtitle": "Pick a folder for ComfyUI's files. We'll also set up Python there automatically.",
+      "pathPlaceholder": "/Users/username/Documents/ComfyUI",
+      "migrationPathPlaceholder": "Select existing ComfyUI installation (optional)",
+      "migrateFromExisting": "Migrate from existing installation",
+      "migrateDescription": "Copy or link your existing models, custom nodes, and configurations from a previous ComfyUI installation.",
+      "chooseDownloadServers": "Choose download servers manually",
+      "downloadServersDescription": "Select specific mirror servers for downloading Python, PyPI packages, and PyTorch based on your location."
+    },
     "systemLocations": "System Locations",
     "failedToSelectDirectory": "Failed to select directory",
     "pathValidationFailed": "Failed to validate path",
@@ -490,18 +512,26 @@
     "metricsDisabled": "Metrics Disabled",
     "updateConsent": "You previously opted in to reporting crashes. We are now tracking event-based metrics to help identify bugs and improve the app. No personal identifiable information is collected."
   },
+  "desktopStart": {
+    "initialising": "Initialising..."
+  },
   "serverStart": {
+    "title": "Starting ComfyUI",
     "troubleshoot": "Troubleshoot",
     "reportIssue": "Report Issue",
     "openLogs": "Open Logs",
     "showTerminal": "Show Terminal",
     "copySelectionTooltip": "Copy selection",
     "copyAllTooltip": "Copy all",
+    "errorMessage": "Unable to start ComfyUI Desktop",
+    "installation": {
+      "title": "Installing ComfyUI"
+    },
     "process": {
       "initial-state": "Loading...",
       "python-setup": "Setting up Python Environment...",
       "starting-server": "Starting ComfyUI server...",
-      "ready": "Finishing...",
+      "ready": "Loading Human Interface",
       "error": "Unable to start ComfyUI Desktop"
     }
   },