fix(perf): fix admin panel 30s load + add loader + abort controller

1. Replace serveStatic with Bun.file() to fix Content-Length: 0 bug
   that caused Nginx to wait 12-30s per file.
2. Add section loader (spinner + 'Cargando...') while sections load.
3. Add AbortController to cancel previous fetch when switching menus.
4. Add credentials: 'same-origin' to ensure cookies are sent.
5. Add error handling for empty responses and HTTP errors.

Fixes: admin panel empty sections, 30s menu load, DOMException aborts.

Refs: production server tenerifeprop.es

public/admin.html

@@ -52,6 +52,31 @@
             box-sizing: border-box;
         }
 
+        /* Section Loader */
+        .section-loader {
+            display: flex;
+            flex-direction: column;
+            align-items: center;
+            justify-content: center;
+            min-height: 400px;
+            gap: 16px;
+        }
+        .section-loader .loader-spinner {
+            width: 48px;
+            height: 48px;
+            border: 3px solid var(--card-border);
+            border-top-color: var(--primary);
+            border-radius: 50%;
+            animation: loader-spin 0.8s linear infinite;
+        }
+        .section-loader p {
+            color: var(--text-muted);
+            font-size: 14px;
+        }
+        @keyframes loader-spin {
+            to { transform: rotate(360deg); }
+        }
+
         html, body {
             height: 100%;
         }
@@ -1285,7 +1310,10 @@
 
         <main class="page-content">
             <div id="admin-content">
-                <!-- Sections loaded dynamically via JavaScript -->
+                <div id="section-loader" class="section-loader" style="display:none">
+                    <div class="loader-spinner"></div>
+                    <p>Cargando...</p>
+                </div>
             </div>
         </main>
     </div>

public/js/admin.js

@@ -66,25 +66,50 @@ class AdminPanel {
     })
   }
 
+  getLoader() {
+    return document.getElementById('section-loader')
+  }
+
+  showLoader(show) {
+    const loader = this.getLoader()
+    if (loader) loader.style.display = show ? 'flex' : 'none'
+  }
+
   async loadSection(section) {
     const content = document.getElementById('admin-content')
     if (!content) return
     
+    // Abort any ongoing fetch to prevent race conditions
+    if (this._abortController) this._abortController.abort()
+    this._abortController = new AbortController()
+    
     // Hide all sections
     content.querySelectorAll('.page-section').forEach(s => s.classList.remove('active'))
     
     // If section not loaded yet, fetch it
     let sec = document.getElementById(`section-${section}`)
     if (!sec) {
+      this.showLoader(true)
       try {
-        const res = await fetch(`/admin/${section}.html`)
+        const res = await fetch(`/admin/${section}.html`, {
+          signal: this._abortController.signal,
+          credentials: 'same-origin'
+        })
+        if (!res.ok) throw new Error(`HTTP ${res.status}`)
         const html = await res.text()
+        if (!html || html.length < 50) throw new Error('Empty response')
         content.insertAdjacentHTML('beforeend', html)
         sec = document.getElementById(`section-${section}`)
-        if (!sec) return
+        if (!sec) throw new Error('Section not found in response')
       } catch (e) {
-        console.error(`Failed to load section: ${section}`, e)
+        if (e.name === 'AbortError') {
+          console.warn(`Section ${section} load aborted`)
+        } else {
+          console.error(`Failed to load section: ${section}`, e)
+        }
         return
+      } finally {
+        this.showLoader(false)
       }
     }
     sec.classList.add('active')

src/server/index.ts

@@ -1794,29 +1794,29 @@ const adminHtmlAuthDisabled = async (c: any, next: any) => {
 }
 
 // Serve static files and SPA routes (clean URLs without .html)
-// Admin component files - serve explicitly BEFORE the /admin route
-app.get('/admin/sidebar.html', serveStatic({ path: './public/admin/sidebar.html' }))
-app.get('/admin/topbar.html', serveStatic({ path: './public/admin/topbar.html' }))
-app.get('/admin/dashboard.html', serveStatic({ path: './public/admin/dashboard.html' }))
-app.get('/admin/properties.html', serveStatic({ path: './public/admin/properties.html' }))
-app.get('/admin/leads.html', serveStatic({ path: './public/admin/leads.html' }))
-app.get('/admin/testimonials.html', serveStatic({ path: './public/admin/testimonials.html' }))
-app.get('/admin/faq.html', serveStatic({ path: './public/admin/faq.html' }))
-app.get('/admin/services.html', serveStatic({ path: './public/admin/services.html' }))
-app.get('/admin/settings.html', serveStatic({ path: './public/admin/settings.html' }))
-app.get('/admin/users.html', serveStatic({ path: './public/admin/users.html' }))
-app.get('/admin/analytics.html', serveStatic({ path: './public/admin/analytics.html' }))
-app.get('/admin/traffic.html', serveStatic({ path: './public/admin/traffic.html' }))
+// Admin component files - using Bun.file() directly to avoid serveStatic content-length bug
+app.get('/admin/sidebar.html', async (c) => new Response(Bun.file('./public/admin/sidebar.html')))
+app.get('/admin/topbar.html', async (c) => new Response(Bun.file('./public/admin/topbar.html')))
+app.get('/admin/dashboard.html', async (c) => new Response(Bun.file('./public/admin/dashboard.html')))
+app.get('/admin/properties.html', async (c) => new Response(Bun.file('./public/admin/properties.html')))
+app.get('/admin/leads.html', async (c) => new Response(Bun.file('./public/admin/leads.html')))
+app.get('/admin/testimonials.html', async (c) => new Response(Bun.file('./public/admin/testimonials.html')))
+app.get('/admin/faq.html', async (c) => new Response(Bun.file('./public/admin/faq.html')))
+app.get('/admin/services.html', async (c) => new Response(Bun.file('./public/admin/services.html')))
+app.get('/admin/settings.html', async (c) => new Response(Bun.file('./public/admin/settings.html')))
+app.get('/admin/users.html', async (c) => new Response(Bun.file('./public/admin/users.html')))
+app.get('/admin/analytics.html', async (c) => new Response(Bun.file('./public/admin/analytics.html')))
+app.get('/admin/traffic.html', async (c) => new Response(Bun.file('./public/admin/traffic.html')))
 
-// SPA routes
-app.get('/property/*', serveStatic({ path: './public/property.html' }))
-app.get('/catalog', serveStatic({ path: './public/catalog.html' }))
-app.get('/catalog.html', serveStatic({ path: './public/catalog.html' }))
-app.get('/admin', serveStatic({ path: './public/admin.html' }))
-app.get('/login', serveStatic({ path: './public/login.html' }))
+// SPA routes - using Bun.file() for static files to avoid content-length bugs
+app.get('/property/*', async (c) => new Response(Bun.file('./public/property.html')))
+app.get('/catalog', async (c) => new Response(Bun.file('./public/catalog.html')))
+app.get('/catalog.html', async (c) => new Response(Bun.file('./public/catalog.html')))
+app.get('/admin', async (c) => new Response(Bun.file('./public/admin.html')))
+app.get('/login', async (c) => new Response(Bun.file('./public/login.html')))
 
 // Fallback to index.html for all other routes
-app.get('*', serveStatic({ path: './public/index.html' }))
+app.get('*', async (c) => new Response(Bun.file('./public/index.html')))
 
 // Start server
 const port = parseInt(process.env.PORT || '8080')