Web dashboard step 7: docs, users page, polish

Users page, README and config.example updates, implementation notes, the
rollout runbook, site-layout 404/500 pages, human-readable download sizes,
dark-mode and narrow-screen polish, and a smoke test over every dashboard
route; also removes zdiff3 ancestor markers left by earlier merges.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NHyYupFdBiR4VfoUM7NjSM

src/web/templates/dashboard/users.html

@@ -0,0 +1,15 @@
+{% extends "layout.html" %}{% block content %}<section class="dashboard">
+<h1>Users</h1>
+<p class="muted">Accounts are read-only here. Create, change, disable, enable, or sign out users with the <code>daily-epub users</code> CLI on the server.</p>
+<div class="scroll-x"><table data-filter>
+<thead><tr><th>Username</th><th>Role</th><th>Status</th><th>Created</th><th>Last login</th><th class="num">Open sessions</th></tr></thead>
+<tbody>{% for user in users %}<tr>
+<td>{{ user.username }}</td>
+<td><span class="badge">{{ user.role }}</span></td>
+<td>{% if user.disabled %}<span class="badge down">disabled</span>{% else %}<span class="badge loved">enabled</span>{% endif %}</td>
+<td>{{ user.created }}</td>
+<td>{{ user.last_login }}</td>
+<td class="num">{{ user.open_sessions }}</td>
+</tr>{% endfor %}{% if users.is_empty() %}<tr><td colspan="6">No users. Bootstrap an admin with <code>daily-epub users add &lt;username&gt; --admin</code>.</td></tr>{% endif %}</tbody>
+</table></div>
+</section>{% endblock %}