feat(design): 主色改靛蓝 #4F46E5，Web 与安卓及 Logo 同步

- primary 换成 Indigo 阶（600 即 #4F46E5），中性色转 Slate 轴、纸面更冷更白
- 实心主色面（主按钮、工作区选中）用 600，链接/浅底文字仍用 700 保对比度
- 信息色 sky 调深到 #16697C，与靛蓝同屏能分清
- Logo / favicon / PWA 图标 / 安卓自适应图标统一为靛蓝底 + 白线 + 淡紫点，tools/make-icons.py 重新生成
- 文档与 e2e 断言同步（主题色 #4f46e5）

web/src/components/icons.tsx

@@ -290,13 +290,13 @@ export const Spinner = ({ size = 16, className = "" }: { size?: number; classNam
 
 export const Logo = ({ size = 28 }: { size?: number }) => (
   <svg width={size} height={size} viewBox="0 0 32 32" aria-hidden>
-    <rect width="32" height="32" rx="9" fill="#274B73" />
+    <rect width="32" height="32" rx="9" fill="#4F46E5" />
     <path
       d="M9 11.5h14M9 16h9.5M9 20.5h6"
-      stroke="#EAF3FB"
+      stroke="#FFFFFF"
       strokeWidth="2"
       strokeLinecap="round"
     />
-    <circle cx="23" cy="20.5" r="3" fill="#5CA8E8" />
+    <circle cx="23" cy="20.5" r="3" fill="#C7D2FE" />
   </svg>
 );

web/src/index.css

@@ -72,7 +72,7 @@
       disabled:pointer-events-none disabled:opacity-40;
   }
   .btn-primary {
-    @apply btn bg-primary-700 text-white shadow-sm hover:bg-primary-800 active:translate-y-px;
+    @apply btn bg-primary-600 text-white shadow-sm hover:bg-primary-700 active:translate-y-px;
   }
   .btn-ghost {
     @apply btn border border-line-200 bg-white text-ink-700 hover:border-line-300 hover:bg-paper-50;
@@ -157,8 +157,8 @@
     scrollbar-width: none;
   }
   .grid-lines {
-    background-image: linear-gradient(to right, rgba(22, 28, 26, 0.04) 1px, transparent 1px),
-      linear-gradient(to bottom, rgba(22, 28, 26, 0.04) 1px, transparent 1px);
+    background-image: linear-gradient(to right, rgba(15, 23, 42, 0.04) 1px, transparent 1px),
+      linear-gradient(to bottom, rgba(15, 23, 42, 0.04) 1px, transparent 1px);
     background-size: 32px 32px;
   }
 }
@@ -443,6 +443,6 @@
 .rich-text .vditor-hint {
   border-color: theme("colors.line.200");
   border-radius: 10px;
-  box-shadow: 0 12px 32px -12px rgba(31, 42, 40, 0.28);
+  box-shadow: 0 12px 32px -12px rgba(15, 23, 42, 0.28);
   font-size: 0.8rem;
 }

web/src/pages/Workspace.tsx

@@ -157,7 +157,7 @@ export function WorkspacePage() {
                     <span
                       className={`pill ${
                         m.role === "owner"
-                          ? "bg-primary-700 text-white"
+                          ? "bg-primary-600 text-white"
                           : m.role === "admin"
                             ? "bg-primary-50 text-primary-700"
                             : "bg-paper-200 text-ink-600"