Add fediverse social features: followers/following lists, actor timelines

Adds get_followers_paginated and get_actor_timeline to FederationService
protocol + SQL implementation + stubs. Includes accumulated federation
changes: models, DTOs, delivery handler, webfinger, inline publishing,
widget nav templates, and migration.

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

browser/templates/_types/day/_nav.html

@@ -25,6 +25,15 @@
   {% endcall %}
 </div>
 
+{# Container nav widgets (market links, etc.) #}
+{% if container_nav_widgets %}
+  {% for wdata in container_nav_widgets %}
+    {% with ctx=wdata.ctx %}
+      {% include wdata.widget.template with context %}
+    {% endwith %}
+  {% endfor %}
+{% endif %}
+
 {# Admin link #}
 {% if g.rights.admin %}
     {% from 'macros/admin_nav.html' import admin_nav_item %}

browser/templates/_types/entry/_nav.html

@@ -22,6 +22,14 @@
   {% endcall %}
 </div>
 
+{% if container_nav_widgets %}
+  {% for wdata in container_nav_widgets %}
+    {% with ctx=wdata.ctx %}
+      {% include wdata.widget.template with context %}
+    {% endwith %}
+  {% endfor %}
+{% endif %}
+
 {# Admin link #}
 {% if g.rights.admin %}