fix: resolve all ESLint errors blocking CI releases

- Extract ThemeContext and ToolCollapseContext definitions into separate
  files to satisfy react-refresh/only-export-components rule
- Move useTheme and useToolCollapse hooks to dedicated hook files
- Fix empty catch block in ThemeContext (add comment)
- Replace Date.now() ref in ThinkingIndicator with useState initializer
- Update all imports across components

Closes feedback #58

src/components/Chat.tsx

@@ -6,7 +6,7 @@ import type { ChatMessage, ConnectionStatus } from '../types';
 import { Bot, ArrowDown, Loader2, ChevronsDownUp, ChevronsUpDown } from 'lucide-react';
 import { useT } from '../hooks/useLocale';
 import { getLocale, type TranslationKey } from '../lib/i18n';
-import { useToolCollapse } from '../contexts/ToolCollapseContext';
+import { useToolCollapse } from '../hooks/useToolCollapse';
 
 interface Props {
   messages: ChatMessage[];