Add fullscreen editor and proportional resize

Introduce a fullscreen editor mode and a proportional resize handle for the memo editor. Updates include:

- UI: add fullscreen button and resize handle to popup.html and related i18n keys for en/ja/ko/zh_CN.
- CSS: styles for .memo-editor, fullscreen state, and #editor-resize-handle, plus layout tweaks for fullscreen.
- Background: enhance context menu handler to retrieve selection text from the active tab using chrome.scripting.executeScript, support opening the extension popup programmatically (tryOpenActionPopup), and factor appendContent logic.
- Oper: implement isFullscreenMode(), openFullscreenTab(), proportional editor resize logic with pointer events (initProportionalEditorResize), focus handling adjustments, and init call. Added helper focusTextareaToEnd().
- Manifest: request scripting and windows permissions required for selection injection and window focus.

These changes enable sending accurate selection text from web pages, allow users to open a fullscreen editor tab, and provide a draggable, proportional resize experience in the popup editor.

popup.html

@@ -51,6 +51,7 @@
     </div>
 
     <div class="memo-editor">
+      <button id="fullscreen" class="action-btn" type="button"></button>
       <textarea
         class="common-editor-inputer"
         rows="4"
@@ -59,6 +60,7 @@
         placeholder=""
         required=""
       ></textarea>
+      <div id="editor-resize-handle" aria-label="Resize"></div>
     </div>
 
   <div class="common-tools-wrapper">