Extract config structs into pkg/probodconfig

probod-bootstrap only needs the config struct definitions for
YAML marshaling but transitively pulled in ~40 heavy runtime
dependencies via pkg/probod. Move all config types and their
methods to a new pkg/probodconfig package and re-export them
from pkg/probod via type aliases for backward compatibility.

Signed-off-by: Émile Ré <emile@getprobo.com>

pkg/probodconfig/notifications_config.go

@@ -0,0 +1,26 @@
+// Copyright (c) 2026 Probo Inc <hello@getprobo.com>.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+package probodconfig
+
+type NotificationsConfig struct {
+	Mailer  MailerConfig  `json:"mailer"`
+	Slack   SlackConfig   `json:"slack"`
+	Webhook WebhookConfig `json:"webhook"`
+}
+
+type WebhookConfig struct {
+	SenderInterval int `json:"sender-interval"`
+	CacheTTL       int `json:"cache-ttl"`
+}