perf: optimize data path, indexes and frontend virtualization

- Убран latestCDNRowsBySource; expanded BIRD preview генерируется on-demand
- Batch AS meta updates; миграция perf-индексов 000012
- VirtualPrefixList для preview префиксов; метрики pipeline refresh
- PolitePause для RIPEstat после cache miss

Co-authored-by: Cursor <cursoragent@cursor.com>

migrations/sqlite/000012_perf_indexes.down.sql

@@ -0,0 +1,6 @@
+DROP INDEX IF EXISTS idx_rev_mat_prefix_rev_id;
+DROP INDEX IF EXISTS idx_config_revision_tenant_module_created;
+DROP INDEX IF EXISTS idx_bgp_speaker_published;
+DROP INDEX IF EXISTS idx_bgp_speaker_last_applied;
+DROP INDEX IF EXISTS idx_module_default_community;
+DROP INDEX IF EXISTS idx_module_doh_profile_id;