添加首页背景图（50%不透明度），重构1.2场地分析为两个子板块（自然地理9图+经济人口1图）

css/style.css

@@ -141,40 +141,27 @@ body {
    Hero区域
    ======================================== */
 .hero {
-    min-height: 100vh;
-    display: flex;
-    align-items: center;
-    justify-content: center;
-    background: linear-gradient(135deg, var(--bg-primary) 0%, var(--bg-secondary) 100%);
-    padding: 6rem 2rem 4rem;
-    text-align: center;
+    position: relative;
+    overflow: hidden;
+}
+
+.hero-background {
+    position: absolute;
+    top: 0;
+    left: 0;
+    right: 0;
+    bottom: 0;
+    background-image: url('../images/hero-bg.jpg');
+    background-size: cover;
+    background-position: center;
+    background-repeat: no-repeat;
+    opacity: 0.5;
+    z-index: 0;
 }
 
 .hero-content {
-    max-width: 800px;
-}
-
-.hero-title {
-    font-size: 3rem;
-    font-weight: 700;
-    color: var(--text-primary);
-    margin-bottom: 1.5rem;
-    letter-spacing: 2px;
-    line-height: 1.3;
-}
-
-.hero-subtitle {
-    font-size: 1.5rem;
-    color: var(--primary-color);
-    margin-bottom: 1rem;
-    font-weight: 500;
-    letter-spacing: 3px;
-}
-
-.hero-description {
-    font-size: 1.1rem;
-    color: var(--text-secondary);
-    letter-spacing: 1px;
+    position: relative;
+    z-index: 1;
 }
 
 /* ========================================
@@ -756,3 +743,48 @@ body {
         height: 350px;  /* 手机端更高 */
     }
 }
+
+/* ========================================
+   前期分析 - 9张图片网格布局
+   ======================================== */
+.analysis-grid-9 {
+    /* 3列布局，9张图 */
+    grid-template-columns: repeat(3, 1fr) !important;
+    gap: var(--spacing-md);
+}
+
+/* 响应式：平板设备改为2列 */
+@media (max-width: 1024px) {
+    .analysis-grid-9 {
+        grid-template-columns: repeat(2, 1fr) !important;
+    }
+}
+
+/* 响应式：手机设备改为1列 */
+@media (max-width: 768px) {
+    .analysis-grid-9 {
+        grid-template-columns: 1fr !important;
+    }
+    
+    .analysis-img {
+        height: 250px;
+    }
+}
+
+/* ========================================
+   前期分析 - 单张大图布局
+   ======================================== */
+.analysis-grid-single {
+    display: flex;
+    justify-content: center;
+    margin-top: var(--spacing-md);
+}
+
+.single-card {
+    max-width: 1000px;
+    width: 100%;
+}
+
+.analysis-img.wide {
+    height: 450px;
+}