feat: Phase 4 — dynamic nav + service visibility based on installed services

Email, calendar, and files no longer appear in the nav or as usable pages
unless they are installed. The nav refreshes whenever a service is installed
or removed via the new pic-services-changed CustomEvent.

Changes:
- routes/services.py: add GET /api/services/active endpoint
- api.js: add servicesAPI.listActive()
- App.jsx: replace hardcoded coreServiceChildren with dynamic state fetched
  from /api/services/active; SERVICE_META maps ids to nav entry shapes
- ServiceNotInstalledBanner.jsx: new component — admin gets catalog link,
  peer gets "contact admin" message
- EmailPage/CalendarPage/FilesPage: show banner when service not installed
- ServicesIndex.jsx: remove CoreServiceCard + CORE_SERVICES "Built-in"
  section; rename Remove → Uninstall; dispatch pic-services-changed on
  install/uninstall success
- MyServices.jsx: conditionally render service cards based on active list;
  placeholder card when absent; page-level notice when nothing is installed
- tests/test_services_active_endpoint.py: 4 new endpoint tests

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

tests/test_services_active_endpoint.py

@@ -0,0 +1,80 @@
+"""
+Tests for GET /api/services/active endpoint.
+"""
+
+import json
+import sys
+from pathlib import Path
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+sys.path.insert(0, str(Path(__file__).parent.parent / 'api'))
+
+from app import app
+
+
+def _make_registry(active_services):
+    reg = MagicMock()
+    reg.list_active = MagicMock(return_value=active_services)
+    return reg
+
+
+@pytest.fixture()
+def client():
+    app.config['TESTING'] = True
+    with app.test_client() as c:
+        yield c
+
+
+def test_active_returns_200(client):
+    import app as app_module
+    with patch.object(app_module, 'service_registry', _make_registry([])):
+        resp = client.get('/api/services/active')
+    assert resp.status_code == 200
+
+
+def test_active_returns_empty_list_when_nothing_installed(client):
+    import app as app_module
+    with patch.object(app_module, 'service_registry', _make_registry([])):
+        resp = client.get('/api/services/active')
+    data = json.loads(resp.data)
+    assert data == []
+
+
+def test_active_returns_installed_services(client):
+    email_svc = {
+        'id': 'email',
+        'name': 'Email',
+        'subdomain': 'mail',
+        'capabilities': {'has_accounts': True},
+        'config': {},
+    }
+    import app as app_module
+    with patch.object(app_module, 'service_registry', _make_registry([email_svc])):
+        resp = client.get('/api/services/active')
+    data = json.loads(resp.data)
+    assert isinstance(data, list)
+    assert len(data) == 1
+    assert data[0]['id'] == 'email'
+    assert data[0]['name'] == 'Email'
+
+
+def test_active_response_shape(client):
+    """Each entry must have id, name, subdomain, and capabilities keys."""
+    email_svc = {
+        'id': 'email',
+        'name': 'Email',
+        'subdomain': 'mail',
+        'capabilities': {'has_accounts': True},
+        'config': {},
+    }
+    import app as app_module
+    with patch.object(app_module, 'service_registry', _make_registry([email_svc])):
+        resp = client.get('/api/services/active')
+    data = json.loads(resp.data)
+    entry = data[0]
+    assert 'id' in entry
+    assert 'name' in entry
+    assert 'subdomain' in entry
+    assert 'capabilities' in entry