feat(ui): implement OAuth login flow and dashboard components

* Add OAuth login handling in app and UI components
* Create new components for login and dashboard pages
* Refactor sidebar and navigation structure
* Introduce types for access entries and status responses

ui/src/components/auth/LoginInfoPanel.svelte

@@ -0,0 +1,34 @@
+<script lang="ts">
+  const { isOAuthCallback }: { isOAuthCallback: boolean } = $props();
+</script>
+
+<div class="rounded-3xl border border-cyan-400/20 bg-slate-900/80 p-8 shadow-2xl shadow-slate-950/40">
+  <div class="inline-flex items-center gap-2 rounded-full border border-cyan-400/20 bg-cyan-400/10 px-3 py-1 text-sm font-medium text-cyan-200">
+    <span class="h-2 w-2 rounded-full bg-emerald-400"></span>
+    AMCS Control Interface
+  </div>
+  <h1 class="mt-6 text-4xl font-semibold tracking-tight text-white">
+    {#if isOAuthCallback}
+      Completing login
+    {:else}
+      Login
+    {/if}
+  </h1>
+  <p class="mt-3 max-w-2xl text-base leading-7 text-slate-300">
+    Origin-style operator access for the AMCS admin interface. ResolveSpec OAuth is the front door now,
+    not the old login shortcut.
+  </p>
+
+  <div class="mt-8 grid gap-4 sm:grid-cols-2">
+    <div class="rounded-2xl border border-white/10 bg-white/5 p-5">
+      <p class="text-sm uppercase tracking-[0.2em] text-slate-400">Primary module</p>
+      <p class="mt-2 text-2xl font-semibold text-white">Projects</p>
+      <p class="mt-2 text-sm text-slate-400">Projects are the first real admin screen in this rollout.</p>
+    </div>
+    <div class="rounded-2xl border border-white/10 bg-white/5 p-5">
+      <p class="text-sm uppercase tracking-[0.2em] text-slate-400">OAuth path</p>
+      <p class="mt-2 text-2xl font-semibold text-white">ResolveSpec</p>
+      <p class="mt-2 text-sm text-slate-400">Client registration, authorize, callback, token exchange.</p>
+    </div>
+  </div>
+</div>