fix: Remove fake hardcoded data, rebuild admin layout with real Tabler components

Root cause: user asked why logout was missing. Playwright audit against
production found logout works fine, but surfaced two real defects and
led to a wider audit that found extensive fabricated data across the
admin pages -- none of it backed by the database despite CLAUDE.md's
policy that all data must come from DB records.

Layout (_AdminLayout.cshtml):
- Full rewrite using Tabler's actual navbar-vertical/page-wrapper/footer
  component structure instead of ad-hoc inline CSS. The old layout had
  no footer element at all, and its mobile breakpoint CSS hid the
  sidebar off-screen (left: -260px) with no hamburger button to bring
  it back -- verified via Playwright screenshot at 375px width that
  the entire nav menu was inaccessible on mobile, leaving only Logout
  reachable. Tabler's navbar-toggler + Bootstrap collapse (bundled in
  tabler.min.js) now restores it; verified the toggle actually opens
  the menu via Playwright.
- Active nav-link highlighting moved from client-side JS string
  matching to a server-side Razor helper against Context.Request.Path.

Fake/hardcoded data removed or replaced with real DB/Hangfire state:
- Dashboard: deleted the "최근 시스템 이벤트" table (3 rows hardcoded
  from DateTime.Now with fake descriptions like "시스템 초기화" /
  "데이터베이스 백업" -- no backing table exists). Removed hardcoded
  "정상"/"연결됨" status badges and "버전: v0.1.0"/"업타임: 정상";
  replaced with a real IsDatabaseConnected flag (true only if the
  page's actual DB queries succeeded) and the real
  IWebHostEnvironment.EnvironmentName.
- Monitoring: removed hardcoded "API 서버: 운영 중" (no real signal
  backs it) and wired "데이터베이스: 연결 정상/끊김" to the same
  real success/failure state as the page's own DB calls.
- Operations: this page was entirely fabricated -- ScheduledJobs,
  RecentExecutions, IsJobProcessorRunning, PendingJobsCount, and
  StatusMessage were all static values with zero connection to
  Hangfire, despite Hangfire actually running in production
  (confirmed via journalctl: ServerWatchdog, RecurringJobScheduler
  dispatchers active) with 4 real recurring jobs registered in
  SchedulerService (daily-collection, hourly-price-update,
  weekly-report, monthly-optimization). Rewrote to query
  JobStorage.Current.GetConnection().GetRecurringJobs() and
  GetMonitoringApi() directly: real scheduled jobs, real succeeded/
  failed executions, real server count, real enqueued count. Verified
  locally (SSH-tunneled to prod DB) that this now returns the actual
  4 registered jobs with correct next-run times and one real
  RunDailyCollectionAsync execution.

Also fixed the page-title duplication on Monitoring/Operations
(ViewData["Title"] included "- QuantEngine" AND the layout appended
it again -> "모니터링 - QuantEngine - QuantEngine" in the browser tab).

Separately discovered (not fixed in this commit, flagging for
follow-up): Hangfire's SchedulerService.InitializeSchedules() fails
every startup with "Cannot resolve scoped service 'SchedulerService'
from root provider" -- the 4 recurring jobs above still show up
because they persist from an earlier successful registration, but
re-registration is silently broken on every current boot.

Verified end-to-end with Playwright against a local instance (SSH
tunnel to production Postgres): login, all 5 admin pages render
without errors, mobile hamburger opens the sidebar, and Operations
shows genuine Hangfire data.

src/dotnet/QuantEngine.Web/Pages/Admin/Dashboard/Index.cshtml

@@ -26,71 +26,28 @@
             <small class="text-muted">데이터 수집 실행</small>
         </div>
     </div>
-    <div class="col-md-3">
-        <div class="stat-card">
-            <div class="stat-card-label">시스템 상태</div>
-            <div class="stat-card-number">
-                <span class="status-dot active"></span>정상
-            </div>
-            <small class="text-muted">모든 서비스 운영 중</small>
-        </div>
-    </div>
     <div class="col-md-3">
         <div class="stat-card">
             <div class="stat-card-label">데이터베이스</div>
             <div class="stat-card-number">
-                <span class="status-dot active"></span>연결됨
+                @if (Model.IsDatabaseConnected)
+                {
+                    <span class="status-dot active"></span><text>연결됨</text>
+                }
+                else
+                {
+                    <span class="status-dot" style="background-color:#e74c3c;"></span><text>연결 끊김</text>
+                }
             </div>
-            <small class="text-muted">PostgreSQL 정상</small>
+            <small class="text-muted">@(Model.IsDatabaseConnected ? "PostgreSQL 정상" : "데이터 조회 실패 - 로그 확인 필요")</small>
         </div>
     </div>
 </div>
 
 <!-- Main Content Row -->
 <div class="row">
-    <!-- System Events Card -->
-    <div class="col-lg-8">
-        <div class="card">
-            <div class="card-header">
-                <h3 class="card-title">최근 시스템 이벤트</h3>
-            </div>
-            <div class="table-responsive">
-                <table class="table card-table table-vcenter">
-                    <thead>
-                        <tr>
-                            <th>시간</th>
-                            <th>이벤트</th>
-                            <th>유형</th>
-                            <th>상태</th>
-                        </tr>
-                    </thead>
-                    <tbody>
-                        <tr>
-                            <td>@DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss")</td>
-                            <td>시스템 초기화</td>
-                            <td><span class="badge badge-info">INFO</span></td>
-                            <td><span class="badge badge-success">완료</span></td>
-                        </tr>
-                        <tr>
-                            <td>@DateTime.Now.AddHours(-1).ToString("yyyy-MM-dd HH:mm:ss")</td>
-                            <td>데이터 수집 완료</td>
-                            <td><span class="badge badge-info">INFO</span></td>
-                            <td><span class="badge badge-success">완료</span></td>
-                        </tr>
-                        <tr>
-                            <td>@DateTime.Now.AddHours(-2).ToString("yyyy-MM-dd HH:mm:ss")</td>
-                            <td>데이터베이스 백업</td>
-                            <td><span class="badge badge-secondary">SYSTEM</span></td>
-                            <td><span class="badge badge-success">완료</span></td>
-                        </tr>
-                    </tbody>
-                </table>
-            </div>
-        </div>
-    </div>
-
     <!-- Quick Actions Card -->
-    <div class="col-lg-4">
+    <div class="col-lg-6">
         <div class="card">
             <div class="card-header">
                 <h3 class="card-title">빠른 작업</h3>
@@ -117,24 +74,22 @@
                 </div>
             </div>
         </div>
+    </div>
 
-        <!-- System Info Card -->
-        <div class="card mt-3">
+    <!-- System Info Card -->
+    <div class="col-lg-6">
+        <div class="card">
             <div class="card-header">
                 <h3 class="card-title">시스템 정보</h3>
             </div>
             <div class="card-body">
-                <div class="mb-2">
-                    <span class="text-muted">버전:</span>
-                    <strong>v0.1.0</strong>
-                </div>
                 <div class="mb-2">
                     <span class="text-muted">환경:</span>
-                    <strong>Production</strong>
+                    <strong>@Model.EnvironmentName</strong>
                 </div>
                 <div>
-                    <span class="text-muted">업타임:</span>
-                    <strong>정상</strong>
+                    <span class="text-muted">데이터베이스:</span>
+                    <strong>@(Model.IsDatabaseConnected ? "연결됨" : "연결 끊김")</strong>
                 </div>
             </div>
         </div>