feat: add upload policies, daily limits, and storage quotas

- Add environment variables to configure anonymous uploads, daily upload caps, and default user storage limits.
- Update config loader to parse and validate the new settings.
- Implement backend logic to track daily usage and active storage per user.
- Update README and `.env.example` to document the new settings and admin panels.

backend/templates/pages/admin_users.html

@@ -1,15 +1,23 @@
 {{define "admin_users.html"}}{{template "base" .}}{{end}}
 
 {{define "content"}}
-<section class="admin-view" aria-labelledby="admin-users-title">
+<section class="app-shell admin-shell" aria-labelledby="admin-users-title">
+  <aside class="app-sidebar">
+    <a class="sidebar-link" href="/admin">Overview</a>
+    <a class="sidebar-link" href="/admin/files">Files</a>
+    <a class="sidebar-link is-active" href="/admin/users">Users</a>
+    <a class="sidebar-link" href="/admin/settings">Settings</a>
+    <a class="sidebar-link" href="/app">My files</a>
+    <form class="sidebar-logout" action="/admin/logout" method="post">
+      <button class="button button-outline" type="submit">Logout</button>
+    </form>
+  </aside>
+
+  <div class="app-main">
   <div class="admin-header">
     <div>
       <p class="kicker">Operator console</p>
-      <h1 id="admin-users-title">Users</h1>
-    </div>
-    <div class="result-actions">
-      <a class="button button-outline" href="/admin">Overview</a>
-      <a class="button button-outline" href="/admin/files">Files</a>
+      <h1 id="admin-users-title">{{.Data.PageTitle}}</h1>
     </div>
   </div>
 
@@ -37,7 +45,7 @@
       <div class="table-header"><h2>Users</h2><p>Disable accounts or create reset links.</p></div>
       <div class="admin-table-wrap">
         <table class="admin-table">
-          <thead><tr><th>User</th><th>Email</th><th>Role</th><th>Status</th><th>Joined</th><th>Actions</th></tr></thead>
+          <thead><tr><th>User</th><th>Email</th><th>Role</th><th>Status</th><th>Storage</th><th>Today</th><th>Joined</th><th>Actions</th></tr></thead>
           <tbody>
             {{range .Data.Users}}
               <tr>
@@ -45,6 +53,8 @@
                 <td>{{.Email}}</td>
                 <td>{{.Role}}</td>
                 <td><span class="badge">{{.Status}}</span></td>
+                <td>{{.StorageUsed}} / {{.StorageQuota}}</td>
+                <td>{{.DailyUsed}}</td>
                 <td>{{.CreatedAt}}</td>
                 <td class="table-actions">
                   {{if eq .Status "disabled"}}
@@ -53,15 +63,20 @@
                     <form action="/admin/users/{{.ID}}/disable" method="post"><button class="button button-danger" type="submit">Disable</button></form>
                   {{end}}
                   <form action="/admin/users/{{.ID}}/reset" method="post"><button class="button button-outline" type="submit">Reset link</button></form>
+                  <form action="/admin/users/{{.ID}}/quota" method="post">
+                    <input class="compact-input" name="storage_quota_mb" placeholder="Quota MB">
+                    <button class="button button-outline" type="submit">Quota</button>
+                  </form>
                 </td>
               </tr>
             {{else}}
-              <tr><td colspan="6">No users yet.</td></tr>
+              <tr><td colspan="8">No users yet.</td></tr>
             {{end}}
           </tbody>
         </table>
       </div>
     </div>
   </div>
+  </div>
 </section>
 {{end}}