feat: add Google Drive file upload functionality with custom dialog

This commit implements the ability to save Scratch 3.0 projects (.sb3)
to Google Drive with a custom dialog for specifying the filename and
save location, complementing the existing "Load from Google Drive"
functionality.

## New Features

- **Menu Integration**: Added "Save to Google Drive" menu item in File menu
- **Save Dialog**: Custom dialog with filename input and save location selection
- **Folder Selection**: Users can save to My Drive root or select a specific folder
- **File Upload**: Multipart upload using Google Drive Files API v3

## Implementation

### New Components

1. **google-drive-saver-hoc.jsx**: HOC for Google Drive save functionality
   - Manages save dialog state and upload process
   - Converts Ruby code to blocks before saving
   - Provides error handling and user feedback

2. **google-drive-save-dialog.jsx**: Custom save dialog component
   - Filename input with .sb3 extension validation
   - Save location dropdown (My Drive or folder selection)
   - Cancel, Reset, and Save buttons

3. **google-drive-save-dialog.css**: Dialog styling

### Modified Files

1. **google-drive-api.js**: Added upload functionality
   - uploadFile(): Multipart upload to Google Drive
   - showFolderPicker(): Folder selection via Google Picker
   - handleFolderPickerResponse(): Handle folder picker callback

2. **menu-bar.jsx**: Integrated save functionality
   - Added "Save to Google Drive" menu item
   - Integrated GoogleDriveSaverHOC
   - Added GoogleDriveSaveDialog component

3. **ja.js**: Added Japanese translations for all new UI elements

## Technical Details

- Uses existing OAuth 2.0 authentication from GoogleDriveLoaderHOC
- Leverages drive.file scope (already configured)
- Multipart upload with metadata and file content
- Base64 encoding for binary file data
- Folder picker using Google Picker API

## Testing

- ✅ Lint checks pass: npm run test:lint
- Dialog UI follows app.diagrams.net design patterns
- Supports both My Drive root and folder selection

## Related

- Implements feature request from Issue #428
- Built on top of PR #427 (Google Drive load functionality)

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

Co-Authored-By: Claude <[email protected]>

Author: takaokouji

src/components/google-drive-save-dialog/google-drive-save-dialog.css

@@ -0,0 +1,121 @@
+@import "../../css/colors.css";
+@import "../../css/units.css";
+
+.modalContent {
+    min-width: 500px;
+    max-width: 600px;
+}
+
+.body {
+    display: flex;
+    flex-direction: column;
+    padding: 1rem;
+}
+
+.header {
+    font-size: 1.25rem;
+    font-weight: bold;
+    margin-bottom: 1.5rem;
+    color: $text-primary;
+}
+
+.content {
+    display: flex;
+    flex-direction: column;
+    gap: 1rem;
+    margin-bottom: 1.5rem;
+}
+
+.formRow {
+    display: flex;
+    flex-direction: column;
+    gap: 0.5rem;
+}
+
+.label {
+    font-weight: 500;
+    color: $text-primary;
+    font-size: 0.9rem;
+}
+
+.input,
+.select {
+    padding: 0.5rem;
+    border: 1px solid $ui-black-transparent;
+    border-radius: 0.25rem;
+    font-size: 0.9rem;
+    font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
+    width: 100%;
+}
+
+.input:focus,
+.select:focus {
+    outline: none;
+    border-color: $motion-primary;
+}
+
+.input:disabled {
+    background-color: $ui-black-transparent;
+    cursor: not-allowed;
+}
+
+.select {
+    cursor: pointer;
+    background-color: $ui-white;
+}
+
+.selectedFolder {
+    font-size: 0.85rem;
+    color: $text-primary-transparent;
+    font-style: italic;
+    margin-top: 0.25rem;
+}
+
+.footer {
+    display: flex;
+    justify-content: flex-end;
+    gap: 0.5rem;
+    padding-top: 1rem;
+    border-top: 1px solid $ui-black-transparent;
+}
+
+.cancelButton,
+.resetButton,
+.saveButton {
+    padding: 0.5rem 1rem;
+    border: none;
+    border-radius: 0.25rem;
+    font-size: 0.9rem;
+    cursor: pointer;
+    font-weight: 500;
+    transition: background-color 0.2s;
+}
+
+.cancelButton {
+    background-color: $ui-white;
+    color: $text-primary;
+    border: 1px solid $ui-black-transparent;
+}
+
+.cancelButton:hover {
+    background-color: $ui-black-transparent;
+}
+
+.resetButton {
+    background-color: $ui-white;
+    color: $text-primary;
+    border: 1px solid $ui-black-transparent;
+}
+
+.resetButton:hover {
+    background-color: $ui-black-transparent;
+}
+
+.saveButton {
+    background-color: $motion-primary;
+    color: $ui-white;
+}
+
+.saveButton:hover {
+    background-color: $motion-primary-transparent;
+}