feat(mobile): search box in the Select Case picker (#488)

The phone case picker had no way to narrow a long case list, so finding
one meant scrolling a sheet that showed about six rows at a time.

- A search field filters rows by name (every typed word must match, any
  order, case-insensitive), with a "No matching cases" state. Enter picks
  the case when exactly one row is left; Escape clears, then closes.
- The field is not auto-focused, so opening the picker does not raise the
  keyboard. The list holds its unfiltered height while searching so the
  sheet does not jump, and the input is 16px so iOS Safari does not zoom.
- Layout: the sheet padded the home-indicator inset on top of the footer
  already doing so, leaving a dead band under Create New Case; the sheet
  now grows to 80dvh and the list fills it instead of a separate 50vh cap.
- Opening scrolls the list (its own box, not scrollIntoView) to the
  currently selected case.

Co-authored-by: Codeman maintainer <noreply@anthropic.com>

src/web/public/i18n.js

@@ -106,6 +106,8 @@
     'Manage AI Coding tools in persistent tmux sessions.': '在持久化 tmux 会话中管理 AI 编程工具。',
     'Select case': '选择案例',
     'Select Case': '选择案例',
+    'Search cases': '搜索案例',
+    'No matching cases': '没有匹配的案例',
     'All cases': '全部案例',
     'No directory': '未选择目录',
     Run: '运行',