Fix WCAG AA color contrast violations across all pages

Replace incorrect perceived-brightness formula in Stats progress bars
with proper WCAG relative luminance calculation, and convert type bar
colors to hex values for reliable contrast detection. Add light: variant
classes to status badges, yellow/purple text, and admin nav links across
17 files. Darken light-mode status-active token and text-tertiary/muted
tokens. Add aria-labels to admin filter selects and flex-wrap for mobile
overflow on AdminEvolutions.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/index.css

@@ -46,8 +46,9 @@
 
   /* Text on dark */
   --color-text-primary: #e6edf3;
-  --color-text-secondary: #7d8590;
-  --color-text-tertiary: #484f58;
+  --color-text-secondary: #9198a1;
+  --color-text-tertiary: #8b949e;
+  --color-text-muted: #8b949e;
   --color-text-link: #7eb0ce;
 
   /* Borders */
@@ -90,7 +91,8 @@ html[data-theme='light'] {
   /* Text */
   --color-text-primary: #1f2328;
   --color-text-secondary: #656d76;
-  --color-text-tertiary: #8b949e;
+  --color-text-tertiary: #596069;
+  --color-text-muted: #596069;
   --color-text-link: #1a5068;
 
   /* Borders */
@@ -103,8 +105,8 @@ html[data-theme='light'] {
   --color-status-alive-bg: rgba(26, 127, 55, 0.1);
   --color-status-dead: #cf222e;
   --color-status-dead-bg: rgba(207, 34, 46, 0.1);
-  --color-status-active: #1a7f37;
-  --color-status-active-bg: rgba(26, 127, 55, 0.1);
+  --color-status-active: #116b2b;
+  --color-status-active-bg: rgba(17, 107, 43, 0.08);
   --color-status-completed: #0969da;
   --color-status-completed-bg: rgba(9, 105, 218, 0.1);
   --color-status-failed: #cf222e;