Add login functionality with password protection and create login page

static/css/style.css

@@ -520,3 +520,117 @@ header {
 [hidden] {
   display: none !important;
 }
+
+/* =============================================
+   Login Page
+   ============================================= */
+.login-page {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  min-height: 100vh;
+  background: radial-gradient(
+    ellipse at 50% 30%,
+    #1a1a22 0%,
+    var(--bg-primary) 70%
+  );
+}
+
+.login-card {
+  width: 100%;
+  max-width: 380px;
+  padding: 40px 36px;
+  background: var(--bg-secondary);
+  border: 1px solid var(--border);
+  border-radius: var(--radius);
+  box-shadow: var(--shadow);
+}
+
+.login-brand {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: 12px;
+  margin-bottom: 32px;
+}
+
+.login-brand .logo {
+  width: 48px;
+  height: 48px;
+  display: grid;
+  place-items: center;
+  color: var(--accent);
+}
+
+.login-brand .logo svg {
+  width: 100%;
+  height: 100%;
+  fill: var(--accent);
+}
+
+.login-brand h1 {
+  font-size: 20px;
+  font-weight: 700;
+  letter-spacing: 0.5px;
+  color: var(--text-primary);
+}
+
+.login-form {
+  display: flex;
+  flex-direction: column;
+  gap: 14px;
+}
+
+.login-form label {
+  font-size: 13px;
+  font-weight: 600;
+  color: var(--text-secondary);
+  text-transform: uppercase;
+  letter-spacing: 0.8px;
+}
+
+.login-form input[type="password"] {
+  width: 100%;
+  padding: 12px 16px;
+  background: var(--bg-tertiary);
+  border: 1px solid var(--border);
+  border-radius: var(--radius-sm);
+  color: var(--text-primary);
+  font-size: 15px;
+  outline: none;
+  transition:
+    border-color 0.2s,
+    box-shadow 0.2s;
+}
+
+.login-form input[type="password"]:focus {
+  border-color: var(--accent);
+  box-shadow: 0 0 0 3px rgba(227, 25, 55, 0.15);
+}
+
+.login-form button {
+  width: 100%;
+  padding: 12px;
+  background: var(--accent);
+  border: none;
+  border-radius: var(--radius-sm);
+  color: #fff;
+  font-size: 15px;
+  font-weight: 700;
+  cursor: pointer;
+  transition: background 0.15s;
+  margin-top: 4px;
+}
+
+.login-form button:hover {
+  background: var(--accent-hover);
+}
+
+.login-error {
+  font-size: 13px;
+  color: var(--accent);
+  text-align: center;
+  padding: 8px;
+  background: rgba(227, 25, 55, 0.08);
+  border-radius: var(--radius-sm);
+}