Integrate federation app with shared menu/header system

Replace standalone base.html with the shared _types/root layout.
Social pages get a second nav row via _types/social/index.html.
Root / becomes a blank page with shared chrome. Auth pages use
the shared layout without the social nav bar.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

templates/_types/federation/index.html

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+{% extends '_types/root/_index.html' %}
+{% block meta %}{% endblock %}
+{% block content %}{% endblock %}

templates/_types/social/header/_header.html

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+{% import 'macros/links.html' as links %}
+{% macro header_row(oob=False) %}
+  {% call links.menu_row(id='social-row', oob=oob) %}
+    <div class="w-full flex flex-row items-center gap-2 flex-wrap">
+      {% if actor %}
+        <nav class="flex gap-3 text-sm items-center flex-wrap">
+          <a href="{{ url_for('social.home_timeline') }}"
+             class="px-2 py-1 rounded hover:bg-stone-200 {% if request.path == url_for('social.home_timeline') %}font-bold{% endif %}">
+            Timeline
+          </a>
+          <a href="{{ url_for('social.public_timeline') }}"
+             class="px-2 py-1 rounded hover:bg-stone-200 {% if request.path == url_for('social.public_timeline') %}font-bold{% endif %}">
+            Public
+          </a>
+          <a href="{{ url_for('social.compose_form') }}"
+             class="px-2 py-1 rounded hover:bg-stone-200 {% if request.path == url_for('social.compose_form') %}font-bold{% endif %}">
+            Compose
+          </a>
+          <a href="{{ url_for('social.following_list') }}"
+             class="px-2 py-1 rounded hover:bg-stone-200 {% if request.path == url_for('social.following_list') %}font-bold{% endif %}">
+            Following
+          </a>
+          <a href="{{ url_for('social.followers_list') }}"
+             class="px-2 py-1 rounded hover:bg-stone-200 {% if request.path == url_for('social.followers_list') %}font-bold{% endif %}">
+            Followers
+          </a>
+          <a href="{{ url_for('social.search') }}"
+             class="px-2 py-1 rounded hover:bg-stone-200 {% if request.path == url_for('social.search') %}font-bold{% endif %}">
+            Search
+          </a>
+          <a href="{{ url_for('social.notifications') }}"
+             class="px-2 py-1 rounded hover:bg-stone-200 relative {% if request.path == url_for('social.notifications') %}font-bold{% endif %}">
+            Notifications
+            <span hx-get="{{ url_for('social.notification_count') }}" hx-trigger="load, every 30s" hx-swap="innerHTML"
+                  class="absolute -top-2 -right-3 text-xs bg-red-500 text-white rounded-full px-1 empty:hidden"></span>
+          </a>
+          <a href="{{ url_for('actors.profile', username=actor.preferred_username) }}"
+             class="px-2 py-1 rounded hover:bg-stone-200">
+            @{{ actor.preferred_username }}
+          </a>
+        </nav>
+      {% else %}
+        <nav class="flex gap-3 text-sm items-center">
+          <a href="{{ url_for('identity.choose_username_form') }}"
+             class="px-2 py-1 rounded hover:bg-stone-200 font-bold">
+            Choose username
+          </a>
+        </nav>
+      {% endif %}
+    </div>
+  {% endcall %}
+{% endmacro %}

templates/_types/social/index.html

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+{% extends '_types/root/_index.html' %}
+{% block meta %}{% endblock %}
+{% block root_header_child %}
+  {% from '_types/root/_n/macros.html' import index_row with context %}
+  {% call index_row('social-header-child', '_types/social/header/_header.html') %}
+  {% endcall %}
+{% endblock %}
+{% block content %}
+  {% block social_content %}{% endblock %}
+{% endblock %}