feat: config knobs and prompts for evidence verification wave

backend/.env.example

@@ -72,3 +72,9 @@ SMTP_PASSWORD=
 SMTP_FROM=
 SMTP_USE_TLS=true
 SMTP_USE_SSL=false
+
+# Wave 5b evidence verification (vision fact-check of cited sheet text)
+AGENT_VERIFY_MAX_CHECKS=20
+AGENT_VERIFY_SEVERITIES=critical,high
+AGENT_VERIFY_REASONING_EFFORT=low
+VERIFY_MAX_TOKENS=8192