frontend: Iris palette — graphite neutrals + indigo-violet accent

Tokens in globals.css, Tailwind gray/indigo scales remapped so the ~350
legacy raw-class uses follow the palette, light-mode override sheet moved
off slate, map accent hexes updated. Severity hues retuned for AA.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

drb-frontend/tailwind.config.ts

@@ -22,6 +22,17 @@ const config: Config = {
       // work — a bare var() hex gives Tailwind nothing to apply alpha to, and the
       // class silently generates no rule (map overlays rendered see-through).
       colors: {
+        // "Iris" palette: the legacy raw gray-*/indigo-* classes (~350 uses)
+        // resolve to graphite + the brand accent instead of Tailwind's slate-blue
+        // defaults, so un-migrated components match the tokens above.
+        gray: {
+          50: "#F7F7F8", 100: "#EDEDEF", 200: "#E4E4E7", 300: "#C9C9D0", 400: "#A1A1AA",
+          500: "#7A7A85", 600: "#4A4B53", 700: "#2A2B31", 800: "#1A1B1F", 900: "#111214", 950: "#08090A",
+        },
+        indigo: {
+          50: "#F0F1FD", 100: "#E2E4FB", 200: "#C8CCF6", 300: "#A8AEF1", 400: "#8B93F0",
+          500: "#6F79E0", 600: "#5E6AD2", 700: "#4E58B8", 800: "#3F4794", 900: "#313770", 950: "#1C1F42",
+        },
         page:          tok("page"),
         surface:       tok("surface"),
         raised:        tok("raised"),
@@ -51,7 +62,7 @@ const config: Config = {
       boxShadow: {
         card: "0 1px 2px 0 rgb(0 0 0 / 0.4), 0 1px 3px 0 rgb(0 0 0 / 0.3)",
         "card-hover": "0 4px 12px 0 rgb(0 0 0 / 0.45), 0 2px 4px 0 rgb(0 0 0 / 0.3)",
-        glow: "0 0 0 1px rgb(99 102 241 / 0.4), 0 0 24px 0 rgb(99 102 241 / 0.25)",
+        glow: "0 0 0 1px rgb(94 106 210 / 0.4), 0 0 24px 0 rgb(94 106 210 / 0.25)",
       },
       animation: {
         "fade-in": "fade-in 0.4s ease-out",