Add admin dashboard filtering and sorting

Provide stable server-side list queries and focused chart controls so operators can inspect large datasets without misleading partial-page ordering.

src/main/resources/db/migration/V18__admin_filter_sort_indexes.sql

@@ -0,0 +1,26 @@
+CREATE INDEX idx_accounts_restricted_created_id
+    ON accounts (anti_abuse_restricted, created_at, id);
+
+CREATE INDEX idx_credit_ledger_type_created_id
+    ON credit_ledger (entry_type, created_at, id);
+
+CREATE INDEX idx_credit_ledger_user_type_created_id
+    ON credit_ledger (user_id, entry_type, created_at, id);
+
+CREATE INDEX idx_admin_audit_action_outcome_occurred_id
+    ON admin_audit_log (action, outcome, occurred_at, id);
+
+CREATE INDEX idx_admin_audit_outcome_occurred_id
+    ON admin_audit_log (outcome, occurred_at, id);
+
+CREATE INDEX idx_admin_operators_created_id
+    ON admin_operators (created_at, id);
+
+CREATE INDEX idx_admin_operators_role_status_created_id
+    ON admin_operators (role, disabled_at, created_at, id);
+
+CREATE INDEX idx_admin_operators_locked_created_id
+    ON admin_operators (locked_until, created_at, id);
+
+CREATE INDEX idx_admin_operators_last_login_id
+    ON admin_operators (last_login_at, id);