Add Memos API adapter and settings UI

Introduce a Memos API adapter to unify compatibility across API flavors (v020-v021, v023, modern) and probe/detect server flavor. Add js/compat/memosApi.adapter.js and rename existing compat modules (memosApi.v024.js -> memosApi.modern.js, memosApi.v1.js -> memosApi.v020-v021.js) and trim probe from v023. Add settings UI support: new i18n keys in en/ja/ko/zh_CN, settings panel styles in css/main.css, new settings input binding and save flow in js (attachment-only default text persisted). Refactor oper.js to use the adapter for uploads, deletes, tag listing, search and image preview auth handling; add helper functions for attachment-only default text and settings payload. Update i18n bindings, popup, manifest and README changelog accordingly.
closed #5

_locales/ja/messages.json

@@ -23,6 +23,18 @@
   "supportedMemosVersion": {
     "message": "Memos v0.15.0 - 0.27.x に対応"
   },
+  "settingsConnectionTitle": {
+    "message": "接続設定"
+  },
+  "settingsConnectionDesc": {
+    "message": "Memos のURLとアクセストークンを設定します。"
+  },
+  "settingsPostingTitle": {
+    "message": "投稿設定"
+  },
+  "settingsPostingDesc": {
+    "message": "添付ファイルのみ送信時の既定テキスト"
+  },
   "placeApiUrl": {
     "message": "Memos サイトURL"
   },
@@ -50,6 +62,9 @@
   "placeShowInput": {
     "message": "既定の「全員に公開」タグ名"
   },
+  "placeAttachmentOnlyDefaultText": {
+    "message": "添付ファイルのみ送信時の既定テキスト（空欄で内蔵文言を使用）"
+  },
   "uploadedListTitle": {
     "message": "アップロード済みファイル（ドラッグで並べ替え）"
   },