Land CSOC-WP-0006 PageOps: member space/page CRUD, copy, transfer

Thin CONTENT_ROOT content plane (ADR-0003/0004) with space visual field,
product UI for Title/Abstract/Visual, page list sidebar, and tests. Update
capability model and smoke checklist; mark WP-0006 finished.

coulomb_social/templates/spaces/page_transfer.html

@@ -0,0 +1,59 @@
+{% extends "base.html" %}
+{% block title %}Transfer page — {{ space.title }} — {{ site_name }}{% endblock %}
+{% block extra_head %}
+<style>
+  select {
+    width: 100%;
+    padding: 0.5rem 0.75rem;
+    margin-top: 0.25rem;
+    border: 1px solid #ccc;
+    border-radius: 6px;
+    font: inherit;
+    background: #fff;
+  }
+  .form-actions {
+    display: flex;
+    flex-wrap: wrap;
+    gap: 0.75rem;
+    margin-top: 1.25rem;
+    align-items: center;
+  }
+</style>
+{% endblock %}
+{% block content %}
+  <p class="muted" style="margin:0 0 0.5rem;">
+    <a href="{% url 'spaces:detail' space.slug %}?page={{ page_slug }}">← {{ space.title }}</a>
+  </p>
+  <h1>Transfer page</h1>
+  <p class="muted">
+    Move <strong>{{ page_slug }}</strong> out of this space into another space you can access.
+    The source page is removed after a successful move. The space index cannot be transferred.
+  </p>
+
+  {% if not all_spaces %}
+    <div class="card">
+      <p style="margin:0;">No other spaces available. Create another space first, then transfer.</p>
+    </div>
+  {% else %}
+    <form method="post" class="card" style="margin-top:1rem;">
+      {% csrf_token %}
+      <label for="id_dest_space">Destination space</label>
+      <select id="id_dest_space" name="dest_space" required>
+        <option value="">— choose —</option>
+        {% for s in all_spaces %}
+          <option value="{{ s.slug }}">{{ s.title }} ({{ s.slug }})</option>
+        {% endfor %}
+      </select>
+
+      <label for="id_dest_slug">Slug in destination <span class="muted">(optional)</span></label>
+      <input type="text" id="id_dest_slug" name="dest_slug" maxlength="80"
+             value="{{ page_slug }}"
+             pattern="[a-z0-9]+(?:-[a-z0-9]+)*" autocomplete="off">
+
+      <div class="form-actions">
+        <button type="submit" class="btn">Transfer page</button>
+        <a class="btn secondary" href="{% url 'spaces:detail' space.slug %}?page={{ page_slug }}">Cancel</a>
+      </div>
+    </form>
+  {% endif %}
+{% endblock %}