refactor(db): normalize asn prefix cache and ttl cleanup

Строки asn_prefix_cache_row; периодический prune через evobgp-ingest.

Co-authored-by: Cursor <[email protected]>

migrations/postgres/000020_asn_cache_rows.up.sql

@@ -0,0 +1,14 @@
+CREATE TABLE asn_prefix_cache_row (
+    asn     BIGINT NOT NULL REFERENCES asn_prefix_cache (asn) ON DELETE CASCADE,
+    prefix  CIDR NOT NULL,
+    PRIMARY KEY (asn, prefix)
+);
+
+INSERT INTO asn_prefix_cache_row (asn, prefix)
+SELECT apc.asn, t.elem::cidr
+FROM asn_prefix_cache apc
+CROSS JOIN LATERAL jsonb_array_elements_text(apc.prefixes_json) AS t(elem)
+WHERE jsonb_typeof(apc.prefixes_json) = 'array'
+  AND jsonb_array_length(apc.prefixes_json) > 0;
+
+ALTER TABLE asn_prefix_cache DROP COLUMN prefixes_json;