fix: storeFact always bumps updated_at; fix $fresh() wrong column name

ON DUPLICATE KEY UPDATE was not touching updated_at, so if a site's
status didn't change MySQL never fired the ON UPDATE trigger and the
row timestamp stayed 6 days stale. do_server.php's 15-min freshness
window then returned empty sites.

Also fixes $fresh() querying WHERE fact_category= (non-existent column)
instead of WHERE category=, which always returned no rows.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

api/lib/kb_engine.php

@@ -105,7 +105,7 @@ class KBEngine {
         JarvisDB::execute(
             'INSERT INTO kb_facts (category, fact_key, fact_value, host, expires_at)
              VALUES (?,?,?,?,?)
-             ON DUPLICATE KEY UPDATE fact_value=VALUES(fact_value), expires_at=VALUES(expires_at)',
+             ON DUPLICATE KEY UPDATE fact_value=VALUES(fact_value), expires_at=VALUES(expires_at), updated_at=NOW()',
             [$category, $key, $value, $host, $expires]
         );
     }