feat: complete login and user management flow

src/styles/global.css

@@ -3856,6 +3856,82 @@ h3 {
   margin-top: var(--space-2);
 }
 
+.login-page {
+  min-height: 100vh;
+  display: grid;
+  place-items: center;
+  padding: 32px;
+  background:
+    linear-gradient(135deg, rgba(37, 99, 235, 0.08), rgba(16, 185, 129, 0.08)),
+    var(--color-bg);
+}
+
+.login-panel {
+  width: min(440px, 100%);
+  padding: 28px;
+  border: 1px solid var(--color-border);
+  border-radius: 8px;
+  background: var(--color-surface);
+  box-shadow: var(--shadow-lg);
+}
+
+.login-brand {
+  display: flex;
+  align-items: center;
+  gap: 14px;
+  margin-bottom: 24px;
+}
+
+.login-brand > span {
+  width: 48px;
+  height: 48px;
+  display: grid;
+  place-items: center;
+  border-radius: 8px;
+  color: var(--color-primary);
+  background: var(--color-primary-soft);
+}
+
+.login-brand h1 {
+  margin: 0;
+  font-size: 24px;
+}
+
+.login-brand p {
+  margin: 4px 0 0;
+  color: var(--color-text-muted);
+}
+
+.login-form {
+  display: grid;
+  gap: 16px;
+}
+
+.login-captcha-row {
+  display: grid;
+  grid-template-columns: 1fr 136px;
+  gap: 12px;
+  align-items: end;
+}
+
+.login-captcha {
+  height: 40px;
+  border: 1px solid var(--color-border);
+  border-radius: 8px;
+  background: var(--color-surface-muted);
+  color: var(--color-text-strong);
+  font-weight: 700;
+  cursor: pointer;
+}
+
+.login-error {
+  margin: 0;
+  padding: 10px 12px;
+  border-radius: 8px;
+  color: var(--color-danger);
+  background: rgba(239, 68, 68, 0.1);
+}
+
 .system-page {
   gap: 28px;
 }