Add drag and drop support for patch files and bump to v1.0.1

[Copilot]

Implements drag and drop file upload for the textarea input area and upgrades version to 1.0.1.

Changes

Drag and Drop

• Added drag/drop event handlers with counter-based approach to prevent flickering on nested elements
• Visual feedback: green dashed border when dragging over textarea
• Validates file extensions (.patch, .diff, .txt)
• Refactored into shared processFiles() function used by both drag-drop and file upload

i18n

• Updated placeholder text in all locales (en, zh, ja) to mention drag and drop
• Added invalidFileType message for unsupported file drops

Version

• Bumped to 1.0.1 in package.json and both manifest files

Screenshots

Original prompt

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This section details on the original issue you should resolve

<issue_title>功能优化</issue_title>
<issue_description>1. 支持拖拽patch.diff 文件到Input Patch/Diff Content 区域后执行上传和渲染
2. 版本升级到1.0.1</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes 功能优化 #12

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