fix(api): parse Postgres bigint (int8) as Number, not string

duration_ms/file_size are int8; node-postgres returned them as strings,
a footgun for any consumer doing arithmetic/sorting/comparison (already
hand-patched once in playout totals). Register a global int8 type parser
so the API emits real numbers. All such values are < 2^53 (no precision loss).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

services/mam-api/src/db/pool.js

@@ -1,4 +1,16 @@
-import { Pool } from 'pg';
+import { Pool, types } from 'pg';
+
+// node-postgres returns BIGINT (int8, OID 20) as a *string* by default, because
+// a 64-bit integer can exceed JS Number.MAX_SAFE_INTEGER. Our int8 columns
+// (duration_ms, file_size, …) are always well within 2^53, so a string here is
+// pure footgun: it breaks any consumer that does arithmetic or comparison on the
+// value (e.g. `duration_ms + x` silently string-concatenates, sorts go
+// lexicographic, `!ms`/`Math.round` edge cases). Parse int8 to a real Number so
+// the API always emits numeric duration_ms/file_size in its JSON.
+//
+// 20 = int8/bigint OID. Values above Number.MAX_SAFE_INTEGER would lose
+// precision, but no column in this schema ever reaches that range.
+types.setTypeParser(20, (val) => (val === null ? null : parseInt(val, 10)));
 
 // Prefer DATABASE_URL (set in docker-compose) over individual DB_* vars
 const pool = process.env.DATABASE_URL