feat(docs): improve image sizing and add global stylesheet

- Add style.css to head config for global styling
- Refactor image height/width constraints with new classes
- Adjust font size and image ratio thresholds
- Add max-width constraints to prevent overflow

docs/.vitepress/theme/index.js

@@ -99,21 +99,29 @@ export default {
       if (!naturalWidth || !naturalHeight) return
 
       const ratio = naturalHeight / naturalWidth
-      img.classList.remove('img-tall', 'img-very-tall', 'img-ultra-tall')
-      img.style.width = 'auto' // 确保宽度自动，防止拉伸
+      img.classList.remove(
+        'img-tall',
+        'img-very-tall',
+        'img-ultra-tall',
+        'img-limit-width',
+        'img-limit-height'
+      )
 
-      if (ratio > 3) {
+      img.style.maxWidth = ''
+      img.style.maxHeight = ''
+      img.style.width = ''
+      img.style.height = ''
+
+      if (ratio <= 1) {
+        img.classList.add('img-limit-width')
+        return
+      }
+
+      img.classList.add('img-tall')
+      if (ratio > 2.2) {
         img.classList.add('img-ultra-tall')
-        img.style.maxHeight = '250px'
-      } else if (ratio > 2) {
+      } else if (ratio > 1.3) {
         img.classList.add('img-very-tall')
-        img.style.maxHeight = '350px'
-      } else if (ratio > 1.2) {
-        img.classList.add('img-tall')
-        img.style.maxHeight = '450px'
-      } else {
-        // 普通图片重置，避免复用 dom 时残留样式
-        img.style.maxHeight = ''
       }
     }