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

js/i18n.js

@@ -102,10 +102,14 @@ function setTitle(id, messageKey) {
 }
 
 function applyStaticI18n() {
-	setText('saveKey', 'saveBtn')
+	setText('saveSettings', 'saveBtn')
 	setText('saveTag', 'saveBtn')
 
 	setText('supportedMemosVersion', 'supportedMemosVersion')
+	setText('settingsConnectionTitle', 'settingsConnectionTitle')
+	setText('settingsConnectionDesc', 'settingsConnectionDesc')
+	setText('settingsPostingTitle', 'settingsPostingTitle')
+	setText('settingsPostingDesc', 'settingsPostingDesc')
 
 	setPlaceholder('apiUrl', 'placeApiUrl')
 	setPlaceholder('apiTokens', 'placeApiTokens')
@@ -121,6 +125,7 @@ function applyStaticI18n() {
 
 	setPlaceholder('hideInput', 'placeHideInput')
 	setPlaceholder('showInput', 'placeShowInput')
+	setPlaceholder('attachmentOnlyDefaultText', 'placeAttachmentOnlyDefaultText')
 
 	setText('uploadlist-title', 'uploadedListTitle')