feat: Sprint 0 — GoFiber + HTMX + TailwindCSS v4 scaffolding

- Go module: git.tukangketik.id/swanadiva/hostkeeper/v2
- GoFiber v2 server with static, template engine, middleware
- HTMX + Alpine.js (downloaded from CDN)
- TailwindCSS v4 with custom theme (Lumina System colors)
- Custom CSS: dot-grid, glassmorphism, animations, toggle, modal
- Layout template (sidebar nav + header + main)
- Dashboard page with host list, search, filter, view toggle
- Health endpoint: GET /api/health

app/backend/views/partials/nav.html

@@ -0,0 +1,31 @@
+{{define "nav"}}
+<nav class="w-[260px] min-h-screen bg-white/70 backdrop-blur-md border-r border-outline-variant/30 flex flex-col shrink-0">
+  <div class="p-4 border-b border-outline-variant/20">
+    <div class="flex items-center gap-2">
+      <div class="w-8 h-8 rounded-lg bg-primary flex items-center justify-center text-white text-sm font-bold">K</div>
+      <span class="font-bold text-lg text-on-surface">Hostkeeper</span>
+    </div>
+  </div>
+  <div class="flex-1 px-3 py-4 space-y-0.5">
+    {{range .NavItems}}
+    <a href="/{{.ID}}"
+       hx-get="/{{.ID}}" hx-target="#main-content" hx-push-url="true"
+       class="flex items-center gap-3 px-3 py-2 rounded-lg transition-colors text-sm
+              {{if eq $.View .ID}}bg-primary/10 text-primary font-medium
+              {{else}}text-on-surface-variant hover:bg-surface-container-low hover:text-on-surface{{end}}">
+      <span class="w-5 h-5 flex items-center justify-center">{{svg .Icon}}</span>
+      <span>{{.Label}}</span>
+    </a>
+    {{end}}
+  </div>
+  <div class="p-4 border-t border-outline-variant/20">
+    <div class="flex items-center gap-3">
+      <div class="w-8 h-8 rounded-full bg-tertiary/20 flex items-center justify-center text-tertiary text-sm font-semibold">U</div>
+      <div class="flex-1 min-w-0">
+        <p class="text-sm font-medium text-on-surface truncate">User</p>
+        <p class="text-xs text-on-surface-variant truncate">Local</p>
+      </div>
+    </div>
+  </div>
+</nav>
+{{end}}