feat: add methods catalog, detail pages, BMI calculator

- Create 16 diet/weight methods across 5 categories with full content
- Add MethodsPage with search, filters (category/difficulty/effectiveness)
- Add MethodDetailPage with pros/cons, scientific basis, contraindications
- Add BmiCalculatorPage with visual BMI scale
- Create reusable components: Badge, DifficultyBadge, EffectivenessIndicator,
  BookmarkButton, MethodCard, SearchBar, FilterPanel
- Add useLocalStorage and useBookmarks hooks for localStorage persistence
- Set up React Router with all routes

Co-authored-by: Cursor <cursoragent@cursor.com>

src/components/SearchBar.tsx

@@ -0,0 +1,32 @@
+interface SearchBarProps {
+  value: string;
+  onChange: (value: string) => void;
+  placeholder?: string;
+}
+
+export function SearchBar({ value, onChange, placeholder = "Поиск методик..." }: SearchBarProps) {
+  return (
+    <div className="relative">
+      <svg
+        className="absolute left-3.5 top-1/2 h-5 w-5 -translate-y-1/2 text-gray-400 dark:text-gray-500"
+        fill="none"
+        viewBox="0 0 24 24"
+        strokeWidth={1.5}
+        stroke="currentColor"
+      >
+        <path
+          strokeLinecap="round"
+          strokeLinejoin="round"
+          d="m21 21-5.197-5.197m0 0A7.5 7.5 0 1 0 5.196 5.196a7.5 7.5 0 0 0 10.607 10.607Z"
+        />
+      </svg>
+      <input
+        type="search"
+        value={value}
+        onChange={(e) => onChange(e.target.value)}
+        placeholder={placeholder}
+        className="w-full rounded-xl border border-gray-300 bg-white py-3 pl-11 pr-4 text-sm text-gray-900 outline-none transition-colors placeholder:text-gray-400 focus:border-primary-500 focus:ring-2 focus:ring-primary-500/20 dark:border-gray-700 dark:bg-gray-900 dark:text-white dark:placeholder:text-gray-500 dark:focus:border-primary-400"
+      />
+    </div>
+  );
+}