feat: add Terminal Dashboard components and state management

- Implemented DashboardToolbar for managing panel toggles and layout presets.
- Created FloatingPanel for a generic sliding panel interface.
- Developed TerminalGrid for rendering a recursive layout of terminal panes.
- Added TerminalPane to encapsulate individual terminal instances with toolbar actions.
- Introduced layout utilities for managing Allotment layout trees.
- Established Zustand store for terminal grid state management, supporting pane operations and layout resets.

ccw/frontend/src/locales/zh/terminal-dashboard.json

@@ -68,6 +68,25 @@
       "blocked": "已阻塞"
     }
   },
+  "toolbar": {
+    "sessions": "会话",
+    "issues": "问题",
+    "queue": "队列",
+    "inspector": "检查器",
+    "layoutSingle": "单窗格",
+    "layoutSplitH": "左右分割",
+    "layoutSplitV": "上下分割",
+    "layoutGrid": "2×2 网格"
+  },
+  "pane": {
+    "selectSession": "选择会话",
+    "selectSessionHint": "从下拉菜单中选择终端会话",
+    "splitHorizontal": "向右分割",
+    "splitVertical": "向下分割",
+    "clearTerminal": "清屏",
+    "closePane": "关闭窗格",
+    "linkedIssue": "关联问题"
+  },
   "tabBar": {
     "noTabs": "暂无终端会话"
   },