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/identity/dev_login.html

@@ -0,0 +1,30 @@
+{% extends "base.html" %}
+{% block title %}Dev sign-in — {{ site_name }}{% endblock %}
+{% block content %}
+  <h1>Dev sign-in</h1>
+  <p class="muted">
+    DEBUG only. Simulates NetKingdom IAM Profile claims when
+    <code>OIDC_ENABLED=false</code>. Not available in production.
+  </p>
+  <form method="post" class="card">
+    {% csrf_token %}
+    <label>Subject (OIDC sub) *
+      <input type="text" name="subject" required placeholder="user-123" value="dev-user-1">
+    </label>
+    <label>Issuer
+      <input type="text" name="issuer" value="https://local.dev/issuer">
+    </label>
+    <label>Name
+      <input type="text" name="name" value="Dev Member">
+    </label>
+    <label>Email
+      <input type="email" name="email" value="dev@example.com">
+    </label>
+    <label>Preferred username
+      <input type="text" name="preferred_username" value="dev">
+    </label>
+    <p style="margin-top:1.25rem;">
+      <button class="btn" type="submit">Establish session</button>
+    </p>
+  </form>
+{% endblock %}