Initial federation app — ActivityPub server for Rose-Ash

Phase 0+1 of AP integration. New 5th Quart microservice:

Blueprints:
- wellknown: WebFinger, NodeInfo 2.0, host-meta
- actors: AP actor profiles (JSON-LD + HTML), outbox, inbox, followers
- identity: username selection flow (creates ActorProfile + RSA keypair)
- auth: magic link login/logout (ported from blog, self-contained)

Services:
- Registers SqlFederationService (real impl) for federation domain
- Registers real impls for blog, calendar, market, cart
- All cross-domain via shared service contracts

Templates:
- Actor profiles, username selection, platform home
- Auth login/check-email (ported from blog)

Infrastructure:
- Dockerfile + entrypoint.sh (matches other apps)
- CI/CD via Gitea Actions
- shared/ as git submodule

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

templates/federation/choose_username.html

@@ -0,0 +1,53 @@
+{% extends "federation/base.html" %}
+{% block title %}Choose Username — Rose Ash{% endblock %}
+{% block content %}
+<div class="py-8 max-w-md mx-auto">
+  <h1 class="text-2xl font-bold mb-2">Choose your username</h1>
+  <p class="text-stone-600 mb-6">
+    This will be your identity on the fediverse:
+    <strong>@username@{{ config.get('ap_domain', 'rose-ash.com') }}</strong>
+  </p>
+
+  {% if error %}
+    <div class="bg-red-50 border border-red-200 text-red-700 p-3 rounded mb-4">
+      {{ error }}
+    </div>
+  {% endif %}
+
+  <form method="post" class="space-y-4">
+    <div>
+      <label for="username" class="block text-sm font-medium mb-1">Username</label>
+      <div class="flex items-center">
+        <span class="text-stone-400 mr-1">@</span>
+        <input
+          type="text"
+          name="username"
+          id="username"
+          value="{{ username | default('') }}"
+          pattern="[a-z][a-z0-9_]{2,31}"
+          minlength="3"
+          maxlength="32"
+          required
+          autocomplete="off"
+          class="flex-1 border border-stone-300 rounded px-3 py-2 focus:outline-none focus:ring-2 focus:ring-stone-500"
+          hx-get="{{ url_for('identity.check_username') }}"
+          hx-trigger="keyup changed delay:300ms"
+          hx-target="#username-status"
+          hx-include="[name='username']"
+        >
+      </div>
+      <div id="username-status" class="text-sm mt-1"></div>
+      <p class="text-xs text-stone-400 mt-1">
+        3-32 characters. Lowercase letters, numbers, underscores. Must start with a letter.
+      </p>
+    </div>
+
+    <button
+      type="submit"
+      class="w-full bg-stone-800 text-white py-2 px-4 rounded hover:bg-stone-700 transition"
+    >
+      Claim username
+    </button>
+  </form>
+</div>
+{% endblock %}