Initial commit: webmail client (M0/M1)

Three-pane webmail client.
- Backend: FastAPI + async SQLAlchemy + arq worker (Postgres/Redis), IMAP/SMTP
  sync, threading, search, drafts/outbox with undo, attachments, 2FA.
- Frontend: React 18 + Vite + TypeScript + TanStack Query + Tailwind; three-pane
  UI with rich-text composer, light/dark themes, resizable panels.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/tailwind.config.js

@@ -0,0 +1,35 @@
+/** @type {import('tailwindcss').Config} */
+export default {
+  darkMode: "class",
+  content: ["./index.html", "./src/**/*.{ts,tsx}"],
+  theme: {
+    extend: {
+      // Semantic tokens backed by CSS variables (see index.css). Using these
+      // instead of raw grays lets every surface switch with the theme.
+      // Make every `border`/`divide` utility theme-aware by default, so a bare
+      // `border` never falls back to Tailwind's light gray-200 in dark mode.
+      borderColor: {
+        DEFAULT: "rgb(var(--app-border) / <alpha-value>)",
+      },
+      divideColor: {
+        DEFAULT: "rgb(var(--app-border) / <alpha-value>)",
+      },
+      colors: {
+        app: {
+          bg: "rgb(var(--app-bg) / <alpha-value>)",
+          surface: "rgb(var(--app-surface) / <alpha-value>)",
+          elevated: "rgb(var(--app-elevated) / <alpha-value>)",
+          border: "rgb(var(--app-border) / <alpha-value>)",
+          fg: "rgb(var(--app-fg) / <alpha-value>)",
+          muted: "rgb(var(--app-muted) / <alpha-value>)",
+          faint: "rgb(var(--app-faint) / <alpha-value>)",
+          accent: "rgb(var(--app-accent) / <alpha-value>)",
+          "accent-fg": "rgb(var(--app-accent-fg) / <alpha-value>)",
+          hover: "rgb(var(--app-hover) / <alpha-value>)",
+          active: "rgb(var(--app-active) / <alpha-value>)",
+        },
+      },
+    },
+  },
+  plugins: [],
+};