refactor: привести шаблон к правилам стайлгайда

- Архитектура SLM: провайдеры перенесены в infrastructure/mantine, стили в shared/styles
- SVG-спрайты: переход на @gromlab/svg-sprites, добавлен preload в layout
- Стили: переменные и брейкпоинты приведены к базовому набору стайлгайда (rem, Mobile First)
- PostCSS: добавлены postcss-custom-media, postcss-nesting, autoprefixer, @csstools/postcss-global-data
- tsconfig: исправлен алиас shared/* → ./src/shared/*
- Удалены app/styles/, app/providers/, scripts/create-svg-sprite.js, public/img/sprites/
- README переписан на SLM-архитектуру
- Добавлены иконки: clipboard-tick, doctor, people, symptom

package.json

@@ -8,9 +8,12 @@
     "start": "next start",
     "lint": "biome check",
     "format": "biome format --write",
-    "sprite": "node scripts/create-svg-sprite.js"
+    "sprite": "svg-sprites",
+    "predev": "svg-sprites",
+    "prebuild": "svg-sprites"
   },
   "dependencies": {
+    "@gromlab/svg-sprites": "^0.1.4",
     "@mantine/core": "^8.3.18",
     "@mantine/hooks": "^8.3.18",
     "clsx": "^2.1.1",
@@ -22,13 +25,15 @@
   },
   "devDependencies": {
     "@biomejs/biome": "2.2.0",
+    "@csstools/postcss-global-data": "^4.0.0",
     "@types/node": "^20",
     "@types/react": "^19",
     "@types/react-dom": "^19",
-    "colorette": "^2.0.20",
+    "autoprefixer": "^10.5.0",
+    "postcss-custom-media": "^12.0.1",
+    "postcss-nesting": "^14.0.0",
     "postcss-preset-mantine": "^1.18.0",
     "postcss-simple-vars": "^7.0.1",
-    "svg-sprite": "^2.0.4",
     "typescript": "^5"
   }
 }