feat(design): 主色由墨松绿改为景泰蓝蓝系，Logo 与图标同步

纸白底改冷调与主色同轴；语义色 sage/wheat/rust 不变，sky 提亮与主色区分。Logo 三段线改浅蓝白、圆点改亮蓝；favicon/PWA 图标/安卓自适应图标/状态栏一并重绘，新增 tools/make-icons.py 作为唯一出处。

android/app/src/main/java/com/dadao/task/ui/KnowledgeScreen.kt

@@ -329,7 +329,7 @@ private fun KnowledgeBody(text: String) {
                 setTextIsSelectable(true)
                 textSize = 14f
                 setLineSpacing(0f, 1.5f)
-                setTextColor(android.graphics.Color.parseColor("#33443F"))
+                setTextColor(android.graphics.Color.parseColor("#262D39"))
                 markwon.setMarkdown(this, text)
             }
         },

android/app/src/main/java/com/dadao/task/ui/RichTextEditorScreen.kt

@@ -350,7 +350,7 @@ private fun PreviewBody(
                         textSize = 15f
                         setPadding(0, 0, 0, 0)
                         setLineSpacing(0f, 1.5f)
-                        setTextColor(android.graphics.Color.parseColor("#4A5854"))
+                        setTextColor(android.graphics.Color.parseColor("#4E5867"))
                         markwon.setMarkdown(this, text)
                     }
                 },

android/app/src/main/java/com/dadao/task/ui/Theme.kt

@@ -13,22 +13,22 @@ import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.sp
 
 /**
- * 与 Web 端 tailwind.config.js 同一套色板：暖白纸面 + 墨松绿主色 + 陶土橙强调。
+ * 与 Web 端 tailwind.config.js 同一套色板：暖白纸面 + 景泰蓝主色 + 陶土橙强调。
  * 两端看同一张截图时，颜色应该能对上，所以这里的值不要单独调。
  */
-val Paper = Color(0xFFFBF9F6)
-val PaperSunken = Color(0xFFF3F0EA)
-val Line = Color(0xFFE4E0D8)
-val LineStrong = Color(0xFFD3CEC2)
+val Paper = Color(0xFFF9FAFC)
+val PaperSunken = Color(0xFFF3F5F9)
+val Line = Color(0xFFE2E6EC)
+val LineStrong = Color(0xFFD3D9E1)
 
-val Ink = Color(0xFF1F2A28)
-val InkSoft = Color(0xFF4A5854)
-val InkMuted = Color(0xFF7C8985)
+val Ink = Color(0xFF262D39)
+val InkSoft = Color(0xFF4E5867)
+val InkMuted = Color(0xFF6C7788)
 
-val Primary = Color(0xFF2A5A50)
-val PrimaryDeep = Color(0xFF1E443C)
-val PrimarySoft = Color(0xFFE3EDE8)
-val PrimaryTint = Color(0xFFD2E3DB)
+val Primary = Color(0xFF274B73)
+val PrimaryDeep = Color(0xFF1F3B5B)
+val PrimarySoft = Color(0xFFDCE9F7)
+val PrimaryTint = Color(0xFFB9D3EC)
 
 val Clay = Color(0xFFC2703D)
 val ClaySoft = Color(0xFFFBEADF)
@@ -39,8 +39,8 @@ val Wheat = Color(0xFFA97C25)
 val WheatSoft = Color(0xFFF8EED7)
 val Rust = Color(0xFFB04A32)
 val RustSoft = Color(0xFFFBE5DF)
-val Sky = Color(0xFF3E6F91)
-val SkySoft = Color(0xFFE4EEF5)
+val Sky = Color(0xFF2F86B0)
+val SkySoft = Color(0xFFE8F4FA)
 
 private val colors = lightColorScheme(
     primary = Primary,