Implement NetKingdom identity shell for coulomb.social (CSOC-WP-0002)

Django scaffold aligned with the business delivery lane: tenant-keyed
Member model without passwords, identity app as sole OIDC/session
boundary, dev-claims login, authenticated /app/ shell, ADR-0001, and
tests. T01/T02/T05/T06 done; OIDC registration, real user-engine HTTP,
flex-auth, and packaging remain open.

coulomb_social/templates/core/app_home.html

@@ -0,0 +1,17 @@
+{% extends "base.html" %}
+{% block title %}Home — {{ site_name }}{% endblock %}
+{% block content %}
+  <h1>Signed in</h1>
+  <p class="muted">Authenticated shell (CSOC-WP-0002). Content surfaces come later.</p>
+  <div class="card">
+    <h2 style="margin-top:0;">Principal</h2>
+    <dl>
+      <dt>Display name</dt><dd>{{ principal.display_name }}</dd>
+      <dt>Username</dt><dd>{{ principal.username }}</dd>
+      <dt>Tenant</dt><dd>{{ principal.tenant_id }}</dd>
+      <dt>Issuer</dt><dd>{{ principal.issuer }}</dd>
+      <dt>Subject</dt><dd>{{ principal.subject }}</dd>
+      <dt>user-engine id</dt><dd>{{ principal.user_engine_user_id }}</dd>
+    </dl>
+  </div>
+{% endblock %}

coulomb_social/templates/core/landing.html

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+{% extends "base.html" %}
+{% block title %}{{ site_name }} — co-creation{% endblock %}
+{% block content %}
+  <h1>coulomb.social</h1>
+  <p class="muted">
+    Co-creation platform reestablished on the Railiance / NetKingdom stack.
+    Members sign in through platform identity — not Bubble.
+  </p>
+  <p>
+    <a class="btn" href="{% url 'identity:login' %}">Sign in</a>
+  </p>
+  <p class="muted" style="margin-top: 2rem; font-size: 0.85rem;">
+    Tenant: {{ default_tenant_id }} · OIDC:
+    {% if oidc_enabled %}enabled{% else %}dev / not configured{% endif %}
+  </p>
+{% endblock %}