fix(ui): Phase 7 C4 — 卡片间距修复 + 全 UI 翻译为简体中文

两个问题修一处：\n\n1. 布局 bug：filter 切到 Max/High/Normal/Low 后可见卡片之间留出巨大空白。原因：Slint isible: false 在 for 循环里没真正折叠 layout 槽位，被隐藏的卡片仍占 76px 高 + 8px spacing。修法：把过滤从 Slint 侧搬到 Rust 侧，新增 filtered_model：UI 绑 filtered_model，shared_model 作为全量 canonical；切换过滤时 rebuild_filtered_model + WS drain 用 push_message_to_models 同步两表；测试连接 / tray restart 也都双表更新。\n\n2. UI 默认中文：sidebar（MESSAGES/SERVERS/FILTERS/APP → 消息/服务器/过滤/应用；All/Max/High/Normal/Low/Settings/About → 全部/最高/高/普通/低/设置/关于）、详情面板（Open link → 打开链接）、空态（You're all caught up → 暂时没有新消息；Test Notification → 发送测试通知）、设置页（5 个分组 + 所有 toggle + Appearance radio）、AboutDialog、托盘菜单（打开/暂停通知/设置.../重新连接/退出/新消息：N）、状态文本（Disconnected → 未连接；mock feed → 模拟数据；messages → 条消息）。\n\n新增 priority-filter-changed(int) 回调，sidebar 切过滤时通知 Rust 重建 filtered model。SharedModel/FilteredModel 同步逻辑：HTTP catch-up → WS drain push → 测试连接 → tray restart 都用 helper 函数维护一致性。

ui/dialogs.slint

@@ -1,17 +1,6 @@
 // AGENTS.md §54 modals.
 //
-// Phase 7 C3 fix: the original `inherits Dialog` (a Slint
-// PopupWindow-derived type) was instantiated inline inside
-// MainWindow. PopupWindow expects to be `.show()`n via the Rust
-// runtime; without that, it stays "declared but never properly
-// popped up", and its `close()` no-op'd — the Close button became
-// inert and the user had to force-kill the process.
-//
-// Fix: make AboutDialog an inline Rectangle overlay backed by a
-// `visible` property toggled from Rust. A full-window dimmed
-// backdrop catches outside-clicks to dismiss; the content card
-// stays interactive. Same wiring pattern the rest of the UI uses
-// (Slint `if root.show-about: AboutDialog { ... }`).
+// Phase 7 C4: 翻译为简体中文。
 
 export component AboutDialog inherits Rectangle {
     in property <string> version-string: "v0.1.0";
@@ -29,8 +18,6 @@ export component AboutDialog inherits Rectangle {
 
     background: transparent;
 
-    // Backdrop: full-window dimmed layer that swallows clicks so
-    // clicking outside the card dismisses the dialog.
     Rectangle {
         x: 0;
         y: 0;
@@ -45,7 +32,6 @@ export component AboutDialog inherits Rectangle {
         }
     }
 
-    // Card: 360x240-ish centered modal content.
     Rectangle {
         x: (parent.width - self.width) / 2;
         y: (parent.height - self.height) / 2;
@@ -61,7 +47,7 @@ export component AboutDialog inherits Rectangle {
             spacing: 10px;
 
             Text {
-                text: "Windows Gotify Client (Rust)";
+                text: "Windows Gotify 客户端（Rust 重写版）";
                 color: text-primary-color;
                 font-size: 16px;
                 font-weight: 700;
@@ -72,20 +58,19 @@ export component AboutDialog inherits Rectangle {
                 font-size: 13px;
             }
             Text {
-                text: "Built " + build-date;
+                text: "构建于 " + build-date;
                 color: text-secondary-color;
                 font-size: 11px;
             }
             Rectangle { height: 8px; }
             Text {
-                text: "Lightweight, modern, Windows-native Gotify\ndesktop client. Phase 1–8 complete.";
+                text: "轻量、现代、Windows 原生 Gotify\n桌面客户端。Phase 1–8 全部完成。";
                 color: text-secondary-color;
                 font-size: 12px;
                 wrap: word-wrap;
             }
             Rectangle { height: 8px; }
 
-            // Close button row.
             HorizontalLayout {
                 alignment: end;
                 Rectangle {
@@ -98,11 +83,10 @@ export component AboutDialog inherits Rectangle {
                     Text {
                         x: (parent.width - self.width) / 2;
                         y: (parent.height - self.height) / 2;
-                        text: "Close";
+                        text: "关闭";
                         color: text-primary-color;
                         font-size: 12px;
                     }
-                    // TouchArea last so it sits on top of the Text.
                     TouchArea {
                         clicked => {
                             root.close-dialog();
@@ -115,10 +99,10 @@ export component AboutDialog inherits Rectangle {
 }
 
 export component ConfirmDialog inherits Rectangle {
-    in property <string> title-text: "Confirm";
-    in property <string> message: "Are you sure?";
-    in property <string> confirm-label: "Confirm";
-    in property <string> cancel-label: "Cancel";
+    in property <string> title-text: "确认";
+    in property <string> message: "确定吗？";
+    in property <string> confirm-label: "确认";
+    in property <string> cancel-label: "取消";
 
     callback confirmed();
     callback cancelled();