feat(vmis): 租戶自動開通完整流程 + Admin Portal SSO + NC 行事曆訂閱

Backend:
- schedule_tenant: NC 新容器自動 pgsql 安裝 (_nc_db_check 全新容器處理)
- schedule_tenant: NC 初始化加入 Redis + APCu memcache 設定 (修正 OIDC invalid_state)
- schedule_tenant: 新租戶 KC realm 自動設定 accessCodeLifespan=600s (修正 authentication_expired)
- schedule_account: NC Mail 帳號自動設定 (nc_mail_result/nc_mail_done_at)
- schedule_account: NC 台灣國定假日行事曆自動訂閱 (CalDAV MKCALENDAR)
- nextcloud_client: 新增 subscribe_calendar() CalDAV 訂閱方法
- settings: 新增系統設定 API (site_title/version/timezone/SSO/Keycloak)
- models/result: 新增 nc_mail_result, nc_mail_done_at 欄位
- alembic: 遷移 002(system_settings) 003(keycloak_admin) 004(nc_mail_result)

Frontend (Admin Portal):
- 新增完整管理後台 (index/tenants/accounts/servers/schedules/logs/settings/system-status)
- api.js: Keycloak JS Adapter SSO 整合 (PKCE/S256, fallback KC JS 來源, 自動 token 更新)
- index.html: Promise.allSettled 取代 Promise.all，防止單一 API 失敗影響整頁
- 所有頁面加入 try/catch + toast 錯誤處理
- 新增品牌 LOGO 與 favicon

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/admin-portal/css/style.css

@@ -0,0 +1,161 @@
+/* VMIS Admin Portal - Custom Styles */
+
+:root {
+  --sidebar-width: 220px;
+  --sidebar-bg: #1a1d23;
+  --sidebar-active: #0d6efd;
+  --header-height: 56px;
+}
+
+body {
+  font-size: 0.875rem;
+  background: #f5f6fa;
+}
+
+/* ── Sidebar ── */
+#sidebar {
+  width: var(--sidebar-width);
+  min-height: 100vh;
+  background: var(--sidebar-bg);
+  position: fixed;
+  top: 0;
+  left: 0;
+  z-index: 100;
+  display: flex;
+  flex-direction: column;
+}
+
+#sidebar .brand {
+  height: var(--header-height);
+  display: flex;
+  align-items: center;
+  padding: 0 1.2rem;
+  border-bottom: 1px solid rgba(255,255,255,0.08);
+  color: #fff;
+  font-weight: 700;
+  font-size: 1rem;
+  letter-spacing: 0.03em;
+  text-decoration: none;
+}
+
+#sidebar .nav-link {
+  color: rgba(255,255,255,0.65);
+  padding: 0.6rem 1.2rem;
+  border-radius: 0;
+  display: flex;
+  align-items: center;
+  gap: 0.6rem;
+  font-size: 0.85rem;
+  transition: background 0.15s, color 0.15s;
+}
+
+#sidebar .nav-link:hover {
+  color: #fff;
+  background: rgba(255,255,255,0.07);
+}
+
+#sidebar .nav-link.active {
+  color: #fff;
+  background: var(--sidebar-active);
+}
+
+#sidebar .nav-section {
+  color: rgba(255,255,255,0.3);
+  font-size: 0.7rem;
+  text-transform: uppercase;
+  letter-spacing: 0.08em;
+  padding: 1rem 1.2rem 0.3rem;
+}
+
+/* ── Main Content ── */
+#main {
+  margin-left: var(--sidebar-width);
+  min-height: 100vh;
+  display: flex;
+  flex-direction: column;
+}
+
+#topbar {
+  height: var(--header-height);
+  background: #fff;
+  border-bottom: 1px solid #e9ecef;
+  display: flex;
+  align-items: center;
+  padding: 0 1.5rem;
+  position: sticky;
+  top: 0;
+  z-index: 99;
+}
+
+#content {
+  padding: 1.5rem;
+  flex: 1;
+}
+
+/* ── Status Lights ── */
+.light {
+  display: inline-block;
+  width: 12px;
+  height: 12px;
+  border-radius: 50%;
+  vertical-align: middle;
+}
+.light-grey  { background: #aaaaaa; }
+.light-green { background: #28a745; }
+.light-red   { background: #dc3545; }
+
+/* ── DataTable tweaks ── */
+.dataTables_wrapper .dataTables_filter input {
+  border: 1px solid #dee2e6;
+  border-radius: 0.375rem;
+  padding: 0.25rem 0.5rem;
+}
+
+.dataTables_wrapper .dataTables_length select {
+  border: 1px solid #dee2e6;
+  border-radius: 0.375rem;
+  padding: 0.25rem 0.5rem;
+}
+
+table.dataTable thead th {
+  border-bottom: 2px solid #dee2e6;
+  background: #f8f9fa;
+  font-weight: 600;
+  white-space: nowrap;
+}
+
+table.dataTable tbody tr:hover {
+  background: #f0f4ff;
+}
+
+/* ── Cards ── */
+.stat-card {
+  border: none;
+  border-radius: 0.75rem;
+  box-shadow: 0 1px 4px rgba(0,0,0,0.08);
+}
+
+/* ── Availability bar ── */
+.avail-bar {
+  height: 6px;
+  border-radius: 3px;
+  background: #e9ecef;
+  overflow: hidden;
+}
+.avail-fill {
+  height: 100%;
+  border-radius: 3px;
+  background: #28a745;
+  transition: width 0.4s;
+}
+.avail-fill.warn  { background: #ffc107; }
+.avail-fill.danger { background: #dc3545; }
+
+/* ── System status matrix ── */
+.status-matrix .env-col {
+  min-width: 120px;
+  text-align: center;
+}
+
+/* ── Modal ── */
+.modal-header { background: #f8f9fa; }