fix(daily-infra-report): remove vestigial ZULIP_API_KEY requirement, exit non-zero on failed send

1. Remove vestigial ZULIP_API_KEY requirement:
   - /api/v1/server_settings is a PUBLIC endpoint (verified HTTP 200 with or without credential)
   - No Zulip API key is required for this call
   - If a future leg genuinely needs abiba-bot's key, it must prove it with a 200 from
     /api/v1/users/me as abiba-bot and label itself degraded when it cannot
   - Never fall back to the vault's shared ZULIP_API_KEY

2. Make failed sends exit non-zero:
   - A degraded leg (no credential configured) must stay exit 0
   - A failed send (attempted and failed) must exit 1
   - This distinguishes 'not configured' from 'attempted and failed'

Test evidence:
- No-credential run: exit 0, digest still produced
- Wrong password: exit 1, labelled SMTP error
- grep -n ZULIP_API_KEY: only comment reference remains

scripts/daily-infra-report.py

@@ -22,14 +22,12 @@ AUTH = "Authorization: PVEAPIToken=«vault: infrastructure/production PVE_API_TO
 
 ZULIP_SITE = "https://chat.sysloggh.net"
 ZULIP_EMAIL = "abiba-bot@chat.sysloggh.net"
-ZULIP_API_KEY = os.environ.get("ZULIP_API_KEY", "")
-if not ZULIP_API_KEY:
-    ZULIP_AUTH = None
-    DEGRADED_LEGS = ["credential-missing: ZULIP_API_KEY"]
-    print("   ⚠️  Degraded leg: credential-missing: ZULIP_API_KEY", file=sys.stderr)
-else:
-    ZULIP_AUTH = f"{ZULIP_EMAIL}:{ZULIP_API_KEY}"
-    DEGRADED_LEGS = []
+# Note: /api/v1/server_settings is a PUBLIC endpoint (verified HTTP 200 with or without credential).
+# No Zulip API key is required for this call. If a future leg genuinely needs abiba-bot's key,
+# it must prove it with a 200 from /api/v1/users/me as abiba-bot and label itself degraded when it cannot.
+# Never fall back to the vault's shared ZULIP_API_KEY.
+ZULIP_AUTH = None
+DEGRADED_LEGS = []
 
 LITELLM_PUBLIC = "https://litellm.sysloggh.net"
 LITELLM_BACKEND = "192.168.68.116"
@@ -725,6 +723,10 @@ if __name__ == "__main__":
     else:
         print("\n✅ All legs fully credentialed")
     
+    # A failed send must exit non-zero; a degraded leg (no credential) must stay exit 0
+    if not ok:
+        sys.exit(1)
+    
     issues = sum(1 for i in ["red"] if report.get("zulip_ext", {}).get("connected") == False)
     print(f"\n📋 Summary:")
     print(f"   Proxmox: {report['nodes_online']}/{report['node_count']} nodes online")