feat: 升级到 lipgloss/bubbletea v2，实现翻译卡片组件

- 升级 charm.land/lipgloss/v2 v1.1.0 -> v2.0.2
- 升级 charm.land/bubbletea/v2 v1.3.10 -> v2.0.2
- 升级 charm.land/bubbles/v2 -> v2.1.0
- 新增翻译卡片组件：元信息行(Tokens/耗时/模型)、用户输入(碳黑背景)、翻译结果
- 卡片组件间距 5px
- 重构 model.go 适配 v2 API
- 更新 keys.go, messages.go, styles.go

internal/tui/styles.go

@@ -0,0 +1,71 @@
+package tui
+
+import (
+	"charm.land/lipgloss/v2"
+)
+
+var (
+	HeaderStyle = lipgloss.NewStyle().
+			Foreground(lipgloss.Color("#FAFAFA")).
+			Bold(true).
+			Padding(0, 1)
+
+	InputLabelStyle = lipgloss.NewStyle().
+			Foreground(lipgloss.Color("#60A5FA")).
+			Bold(true)
+
+	OutputLabelStyle = lipgloss.NewStyle().
+				Foreground(lipgloss.Color("#34D399")).
+				Bold(true)
+
+	InputTextStyle = lipgloss.NewStyle().
+			Foreground(lipgloss.Color("#E5E7EB"))
+
+	OutputTextStyle = lipgloss.NewStyle().
+			Foreground(lipgloss.Color("#FFFFFF"))
+
+	ErrorTextStyle = lipgloss.NewStyle().
+			Foreground(lipgloss.Color("#F87171")).
+			Bold(true)
+
+	TimestampStyle = lipgloss.NewStyle().
+			Foreground(lipgloss.Color("#6B7280"))
+
+	DividerStyle = lipgloss.NewStyle().
+			Foreground(lipgloss.Color("#374151"))
+
+	StatusBarStyle = lipgloss.NewStyle().
+			Background(lipgloss.Color("#1F2937")).
+			Foreground(lipgloss.Color("#9CA3AF"))
+
+	StatusItemStyle = lipgloss.NewStyle().
+			Foreground(lipgloss.Color("#9CA3AF"))
+
+	StatusValueStyle = lipgloss.NewStyle().
+				Foreground(lipgloss.Color("#FAFAFA"))
+
+	LoadingStyle = lipgloss.NewStyle().
+			Foreground(lipgloss.Color("#60A5FA"))
+
+	StatusDotStyle = lipgloss.NewStyle().
+			Foreground(lipgloss.Color("#34D399"))
+
+	CardStyle = lipgloss.NewStyle().
+			MarginBottom(5)
+
+	CardMetaStyle = lipgloss.NewStyle().
+			Foreground(lipgloss.Color("#6B7280")).
+			Padding(0, 1)
+
+	CardMetaSeparatorStyle = lipgloss.NewStyle().
+				Foreground(lipgloss.Color("#374151")).
+				Render(" │ ")
+
+	CardInputStyle = lipgloss.NewStyle().
+			Background(lipgloss.Color("#1A1A1A")).
+			Foreground(lipgloss.Color("#E5E7EB")).
+			Padding(0, 1)
+
+	CardOutputStyle = lipgloss.NewStyle().
+			Foreground(lipgloss.Color("#FFFFFF"))
+)