M0: Vue 3 + TypeScript frontend — auth views + authed board shell

- Vite + Vue 3.5 + Pinia + vue-router + Tailwind (brand accent #F5C518),
  dark-mode aware, deterministic package-lock.json for `npm ci`.
- Session store (fetchMe/login/register/logout) over a credentials:'include'
  fetch client; router guards (requiresAuth / guestOnly) with lazy /me resolve.
- BaseButton + BaseInput primitives (focus rings, loading, error states).
- LoginView, RegisterView, and an authed BoardView shell with an empty state
  for the M1 masonry board — all at v1 polish (rule 24).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FRgehjoz7Yv8LkUfADxACm

frontend/tailwind.config.js

@@ -0,0 +1,21 @@
+/** @type {import('tailwindcss').Config} */
+export default {
+  darkMode: "media",
+  content: ["./index.html", "./src/**/*.{vue,ts}"],
+  theme: {
+    extend: {
+      colors: {
+        // ThoughtSync accent — a Keep-ish warm yellow.
+        brand: {
+          DEFAULT: "#F5C518",
+          600: "#D9A800",
+          700: "#B98F00",
+        },
+      },
+      fontFamily: {
+        sans: ["Inter", "system-ui", "-apple-system", "sans-serif"],
+      },
+    },
+  },
+  plugins: [],
+};