Change resend to using smtp

Signed-off-by: Asai Neko <sugar@sne.moe>

config.default.yaml

@@ -20,7 +20,12 @@ search:
     host: 127.0.0.1
     api_key: ""
 email:
-    resend_api_key: abc
+    host:
+    port:
+    username:
+    password:
+    security:
+    insecure_skip_verify:
     from:
 secrets:
     jwt_secret: example