Upgrade dependencies to latest stable versions, migrate Tailwind CSS v3 to v4

Bumped React, Supabase JS, and type packages to latest patch/minor releases.
Migrated the Tailwind pipeline from the v3 JS-config format to v4's CSS-first
@theme setup (@tailwindcss/postcss, @import "tailwindcss" in globals.css),
removing tailwind.config.ts and autoprefixer since v4 handles both natively.
All existing color/radius/font tokens were ported 1:1 so no component classes
needed to change. TypeScript and ESLint were bumped and tested against their
true latest majors (7.x and 10.x) but both broke the build/lint pipeline, so
they're pinned to the latest working minor instead (TypeScript 5.9.3, ESLint
9.39.5).

app/globals.css

@@ -1,8 +1,45 @@
-@tailwind base;
-@tailwind components;
-@tailwind utilities;
+@import "tailwindcss";
+
+/* Design tokens from spec §7 (ported from tailwind.config.ts for Tailwind v4) */
+@theme {
+  --color-brand-50: #fdf3f8;
+  --color-brand-100: #fdeaf3;
+  --color-brand-200: #f6cfe2;
+  --color-brand-500: #d6046e;
+  --color-brand-600: #b0035a;
+  --color-brand-700: #a30354;
+
+  --color-surface: #f9f1f5;
+
+  --color-border: #eedde6;
+  --color-border-subtle: #f7e8ef;
+
+  --color-ink: #2d1c26;
+  --color-ink-body: #503b47;
+  --color-ink-muted: #7a636f;
+
+  --color-success-bg: #dff6dd;
+  --color-success-text: #0e700e;
+
+  --color-danger-bg: #fde7e9;
+  --color-danger-text: #b10e1c;
+  --color-danger-solid: #c50f1f;
+
+  --color-warning-bg: #fff4ce;
+  --color-warning-text: #835b00;
+
+  --color-info-bg: #d7f0f0;
+  --color-info-text: #00666d;
+
+  --color-purple-bg: #f0ecf7;
+  --color-purple-text: #5c2e91;
+
+  --radius: 8px;
+
+  --font-sans: var(--font-nunito), system-ui, sans-serif;
+}
 
 body {
-  background-color: theme("colors.surface");
-  color: theme("colors.ink.DEFAULT");
+  background-color: var(--color-surface);
+  color: var(--color-ink);
 }

package.json

@@ -10,21 +10,21 @@
   },
   "dependencies": {
     "@supabase/ssr": "^0.12.1",
-    "@supabase/supabase-js": "^2.110.3",
+    "@supabase/supabase-js": "^2.110.5",
     "lucide-react": "^1.24.0",
     "next": "16.2.10",
-    "react": "19.2.4",
-    "react-dom": "19.2.4"
+    "react": "19.2.7",
+    "react-dom": "19.2.7"
   },
   "devDependencies": {
-    "@types/node": "^20",
-    "@types/react": "^19",
-    "@types/react-dom": "^19",
-    "autoprefixer": "^10.5.2",
-    "eslint": "^9",
+    "@tailwindcss/postcss": "^4.3.2",
+    "@types/node": "^24.13.3",
+    "@types/react": "^19.2.17",
+    "@types/react-dom": "^19.2.3",
+    "eslint": "^9.39.5",
     "eslint-config-next": "16.2.10",
     "postcss": "^8.5.19",
-    "tailwindcss": "^3.4.19",
-    "typescript": "^5"
+    "tailwindcss": "^4.3.2",
+    "typescript": "^5.9.3"
   }
 }

postcss.config.js

@@ -1,6 +1,5 @@
 module.exports = {
   plugins: {
-    tailwindcss: {},
-    autoprefixer: {},
+    "@tailwindcss/postcss": {},
   },
 };

tailwind.config.ts

@@ -1,44 +0,0 @@
-import type { Config } from "tailwindcss";
-
-// Design tokens from spec §7
-const config: Config = {
-  content: ["./app/**/*.{ts,tsx}", "./components/**/*.{ts,tsx}"],
-  theme: {
-    extend: {
-      colors: {
-        brand: {
-          50: "#fdf3f8",
-          100: "#fdeaf3",
-          200: "#f6cfe2",
-          500: "#d6046e",
-          600: "#b0035a",
-          700: "#a30354",
-        },
-        surface: "#f9f1f5",
-        border: {
-          DEFAULT: "#eedde6",
-          subtle: "#f7e8ef",
-        },
-        ink: {
-          DEFAULT: "#2d1c26",
-          body: "#503b47",
-          muted: "#7a636f",
-        },
-        success: { bg: "#dff6dd", text: "#0e700e" },
-        danger: { bg: "#fde7e9", text: "#b10e1c", solid: "#c50f1f" },
-        warning: { bg: "#fff4ce", text: "#835b00" },
-        info: { bg: "#d7f0f0", text: "#00666d" },
-        purple: { bg: "#f0ecf7", text: "#5c2e91" },
-      },
-      borderRadius: {
-        DEFAULT: "8px",
-      },
-      fontFamily: {
-        sans: ["var(--font-nunito)", "system-ui", "sans-serif"],
-      },
-    },
-  },
-  plugins: [],
-};
-
-export default config;