style: fix invalid color refs and standardize hex

Fix invalid SCSS variable syntax in the NoticeMessage component by replacing invalid $text-[#xxx] references with direct hex codes. Replace SCSS color variable usages with hardcoded hex values across multiple UI components. Standardize hex color values to lowercase in the global SCSS file, and fix the trailing newline in src/uni.scss.

src/pages/ChatMain/HomeWelcome/index.vue

@@ -136,7 +136,7 @@ const weatherTextMap = {
   height: 92px;
   padding: 12px 12px 0;
   box-sizing: border-box;
-  background: $theme-color-50;
+  background: #F0F8F3;
 }
 
 .home-welcome-header {
@@ -150,7 +150,7 @@ const weatherTextMap = {
 .home-welcome-title {
   flex: 1;
   min-width: 0;
-  color: $text-[#0B5C2D];
+  color: #0B5C2D;
   font-size: 21px;
   line-height: 28px;
   font-weight: 900;
@@ -159,7 +159,7 @@ const weatherTextMap = {
 .home-welcome-weather {
   flex-shrink: 0;
   margin-left: 12px;
-  color: $text-color-900;
+  color: #181B25;
   font-size: 22px;
   line-height: 26px;
   font-weight: 900;

src/pages/ChatMain/NoticeMessage/index.vue

@@ -105,13 +105,13 @@ const clickItem = (item) => {
 }
 
 .text-color {
-  color: $text-[#0B5C2D];
+  color: #0B5C2D;
 }
 
 .underline-text {
   text-decoration: underline;
-  text-decoration-color: $text-[#35F37F];
-  color: $text-color-400;
+  text-decoration-color: #35F37F;
+  color: #99A0AE;
 }
 
 .noMessage {
@@ -129,7 +129,7 @@ const clickItem = (item) => {
 }
 
 .noMessage-text {
-  color: $text-[#0B5C2D];
+  color: #0B5C2D;
   line-height: 16px;
   white-space: normal;
   overflow-wrap: break-word;

src/pages/Discovery/index.vue

@@ -240,14 +240,14 @@ onMounted(() => {
   width: 100%;
   height: 100%;
   min-height: 0;
-  background: $theme-color-50;
+  background: #F0F8F3;
 }
 
 .discovery-tabs-sticky {
   flex-shrink: 0;
   z-index: 12;
   width: 100%;
-  background: $theme-color-50;
+  background: #F0F8F3;
 }
 
 .discovery-scroll {