Add workspace management foundation

internal/app/templates/workspaces.html

@@ -0,0 +1,18 @@
+{{define "workspaces.html"}}
+{{template "shell-start" .}}
+<header class="page-head"><div><p class="eyebrow">ADMIN</p><h1>Workspaces</h1><p>Create separate spaces for teams and switch between them.</p></div></header>
+{{template "notice" .}}
+<div class="two-column users-layout">
+  <section class="card form-card"><p class="eyebrow">NEW WORKSPACE</p><h2>Create a workspace</h2>
+    <form method="post" action="/admin/workspaces" class="stack-form"><input type="hidden" name="csrf" value="{{.CSRF}}">
+      <label>Workspace name<input name="name" required maxlength="100" placeholder="Product team"></label>
+      <label>Workspace slug<input name="slug" required maxlength="60" pattern="[a-z0-9-]+" placeholder="product-team"><small>Lowercase letters, numbers, and hyphens.</small></label>
+      <button class="button primary full">Create workspace</button>
+    </form>
+  </section>
+  <section class="card"><header class="section-head"><div><p class="eyebrow">YOUR SPACES</p><h2>{{len .Workspaces}} workspaces</h2></div></header>
+    <div class="user-list">{{range .Workspaces}}<div class="user-row"><span class="avatar">▣</span><div><strong>{{.Name}}</strong><small>{{.Slug}}</small></div>{{if eq .ID $.Workspace.ID}}<span class="badge approved">Current</span>{{else}}<form method="post" action="/workspace/switch"><input type="hidden" name="csrf" value="{{$.CSRF}}"><input type="hidden" name="workspace_id" value="{{.ID}}"><button class="text-button" type="submit">Switch</button></form>{{end}}</div>{{end}}</div>
+  </section>
+</div>
+{{template "shell-end" .}}
+{{end}}