feat: vault-aligned server v1 + UX polish

Redesign the optional FastAPI companion around vault files (manifest /
PUT/GET/DELETE + OCR jobs) instead of legacy strokes_json notes. Wire a
client Server settings panel for health/login. Polish shell UX: l10n for
settings/home/board, sticky-board empty state, and a narrow-screen
diagnostics FAB.

Co-authored-by: Cursor <cursoragent@cursor.com>

lib/l10n/app_zh.arb

@@ -169,5 +169,43 @@
   },
   "syncAuto": "启动时自动同步",
   "syncCredentialsNote": "凭据以明文保存在本地，建议使用专用的应用密码。",
-  "syncNotConfigured": "请输入服务器地址以启用同步。"
+  "syncNotConfigured": "请输入服务器地址以启用同步。",
+  "settingsDefaults": "默认笔迹",
+  "settingsAppearance": "外观",
+  "settingsAbout": "关于",
+  "settingsDefaultTool": "默认工具",
+  "settingsDefaultColor": "默认颜色",
+  "settingsDefaultWidth": "默认线宽",
+  "settingsPressureCurve": "压感曲线",
+  "settingsClearConfirmBody": "将重置笔默认值与外观设置。笔记和文档不会受影响。",
+  "serverSection": "BadNote 服务器",
+  "serverUrl": "服务器地址",
+  "serverUrlHint": "http://192.168.1.10:8080",
+  "serverUsername": "用户名",
+  "serverPassword": "密码",
+  "serverSave": "保存并登录",
+  "serverTest": "测试连接",
+  "serverTestOk": "连接成功 · API {version}",
+  "@serverTestOk": {
+    "placeholders": { "version": { "type": "String" } }
+  },
+  "serverTestFail": "连接失败：{error}",
+  "@serverTestFail": {
+    "placeholders": { "error": { "type": "String" } }
+  },
+  "serverLoggedIn": "已登录",
+  "serverHint": "可选。用于自托管 vault 协助同步与延迟 OCR；日常笔记仍完全离线。",
+  "boardEmptyTitle": "还没有便利贴",
+  "boardEmptyBody": "点按右下角添加卡片。在正文写 [[另一张卡片id]] 可建立双链。",
+  "relativeJustNow": "刚刚",
+  "relativeMinutesAgo": "{n} 分钟前",
+  "@relativeMinutesAgo": { "placeholders": { "n": { "type": "int" } } },
+  "relativeHoursAgo": "{n} 小时前",
+  "@relativeHoursAgo": { "placeholders": { "n": { "type": "int" } } },
+  "relativeYesterday": "昨天",
+  "diagExported": "诊断包已导出（{bytes} 字节）\n路径已复制",
+  "@diagExported": { "placeholders": { "bytes": { "type": "int" } } },
+  "diagExportFail": "导出失败：{error}",
+  "@diagExportFail": { "placeholders": { "error": { "type": "String" } } },
+  "processingOcr": "正在识别文字…"
 }