Search and Diff CSS enhancements (#14050)

* Search and Diff CSS enhancements

- Use flexbox for language stats
- Improve labels and code boxes on repo and code search
- Use flexbox on diff header and improve suppressed diff text
- Add dedicated color for diff expander

* more diff tweaks, less vertical padding on header

* more minor tweaks

* always show fold icon, image diff improvments

* remove margin

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

web_src/less/themes/theme-arc-green.less

@@ -82,7 +82,8 @@
   --color-text-dark: #dbe0ea;
   --color-text: #bbc0ca;
   --color-text-light: #a6aab5;
-  --color-text-light-2: #868a95;
+  --color-text-light-2: #8a8e99;
+  --color-text-light-3: #707687;
   --color-footer: #2e323e;
   --color-timeline: #4c525e;
   --color-input-text: #d5dbe6;
@@ -92,7 +93,8 @@
   --color-navbar: #2a2e3a;
   --color-label: #ffffff0d;
   --color-label-hover: #ffffff20;
-  --color-label-basic: #00000016;
+  --color-label-basic: #00000030;
+  --color-label-basic-hover: #40404030;
   --color-label-border: #ffffff28;
   --color-hover: #ffffff0d;
   --color-active: #ffffff14;
@@ -104,6 +106,8 @@
   --color-code-bg: #2a2e3a;
   --color-shadow: #00000060;
   --color-secondary-bg: #2a2e3a;
+  --color-text-focus: #fff;
+  --color-expand-button: #3c404d;
 }
 
 .repository.branches .commit-divergence .bar {
@@ -118,10 +122,6 @@
   background: var(--color-primary-alpha-20) !important;
 }
 
-body {
-  color: var(--color-secondary-dark-6);
-}
-
 ::placeholder,
 .CodeMirror-placeholder {
   color: #6a737d !important;
@@ -505,15 +505,6 @@ td.blob-excerpt {
   background-color: rgba(0, 0, 0, .15);
 }
 
-a.blob-excerpt {
-  color: #ccc;
-  background: #393d4a;
-}
-
-a.blob-excerpt:hover {
-  background: #87ab63;
-}
-
 .lines-code.active,
 .lines-code .active {
   background: #534d1b !important;
@@ -658,18 +649,6 @@ a.blob-excerpt:hover {
   border-right-color: var(--color-secondary) !important;
 }
 
-.repository .diff-detail-box {
-  background-color: #383c4a;
-
-  .detail-files {
-    background-color: inherit;
-  }
-
-  &.sticky {
-    border-bottom-color: var(--color-secondary);
-  }
-}
-
 /* code mirror dark theme */
 
 .CodeMirror {