0.2.45: Administrator (view only) role

New external role administrator_viewer: signs into the admin interface
and reads everything for its granted funds and SPVs (overview, partners,
capital accounts with every investor's statements, documents, valuation
history) but every write is refused: no imports, uploads, deletions,
entity edits, exit marking, or account management. No migration needed;
roles are stored as strings.

Internal admins can flip an Administrator between full management and
view only via a new Access level dropdown in Users > Manage. The
user-list endpoint is read-widened for the viewer role so investor names
resolve on its screens; all mutating endpoints keep the stricter gate.

backend/ten31portal/routers/capital_account_router.py

@@ -76,8 +76,9 @@ def list_statements(
     query = select(CapitalAccountStatement)
     allowed = accessible_entity_ids(user, session)
 
-    if user.role == UserRole.fund_administrator:
-        # An Administrator sees every investor's statements, but only inside their funds.
+    if user.role in (UserRole.fund_administrator, UserRole.administrator_viewer):
+        # An Administrator (managing or view-only) sees every investor's statements,
+        # but only inside their funds.
         if not allowed:
             return []
         query = query.where(col(CapitalAccountStatement.entity_id).in_(allowed))