style: 移除所有圆角并采用古早互联网博客风格

Co-authored-by: aider (deepseek/deepseek-chat) <aider@aider.chat>

static/css/style.css

@@ -27,10 +27,8 @@ body {
     position: sticky;
     top: 0;
     z-index: 100;
-    background: rgba(255, 255, 255, 0.85);
-    backdrop-filter: blur(12px);
-    -webkit-backdrop-filter: blur(12px);
-    border-bottom: 1px solid rgba(0, 0, 0, 0.05);
+    background: #ffffff;
+    border-bottom: 2px solid #000;
     padding: 0.75rem 1.5rem;
 }
 
@@ -85,8 +83,7 @@ body {
 /* ==================== 卡片 ==================== */
 .card {
     background: #ffffff;
-    border-radius: 20px;
-    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.05);
+    border: 2px solid #000;
     overflow: hidden;
     transition: transform 0.2s ease, box-shadow 0.2s ease;
     display: flex;
@@ -209,8 +206,7 @@ body {
 .form-group input[type="text"],
 .form-group input[type="file"] {
     padding: 0.625rem 0.75rem;
-    border: 1px solid #e2e8f0;
-    border-radius: 8px;
+    border: 2px solid #000;
     font-size: 1rem;
     transition: border-color 0.2s;
 }
@@ -226,8 +222,7 @@ body {
 .btn {
     display: inline-block;
     padding: 0.625rem 1.25rem;
-    border: none;
-    border-radius: 8px;
+    border: 2px solid #000;
     font-size: 1rem;
     font-weight: 600;
     cursor: pointer;
@@ -272,7 +267,6 @@ body {
     width: 100%;
     border-collapse: collapse;
     background: #ffffff;
-    border-radius: 12px;
     overflow: hidden;
     box-shadow: 0 2px 8px rgba(0, 0, 0, 0.05);
 }
@@ -308,7 +302,7 @@ body {
     padding: 1.5rem;
     color: #a0aec0;
     font-size: 0.875rem;
-    border-top: 1px solid #e2e8f0;
+    border-top: 2px solid #000;
     margin-top: auto;
 }
 
@@ -334,7 +328,7 @@ body {
 /* ==================== 代码高亮（Pygments 默认主题） ==================== */
 .codehilite {
     background: #f7fafc;
-    border-radius: 8px;
+    border: 2px solid #000;
     padding: 1rem;
     overflow-x: auto;
     margin: 1rem 0;