Add config validation and dashboard

Add YAML config loading with validation, env overrides for secrets, and
a web dashboard exposing health, stats, and recent events.

ntfy.v

@@ -0,0 +1,76 @@
+module main
+
+import net.http
+import time
+import sources
+
+pub struct NtfyClient {
+pub mut:
+	base_url   string
+	auth_token string
+	logger     Logger
+}
+
+pub fn new_ntfy_client(cfg ServerConfig, logger Logger) NtfyClient {
+	return NtfyClient{
+		base_url:   cfg.url.trim_right('/')
+		auth_token: cfg.auth_token
+		logger:     logger
+	}
+}
+
+fn join_tags(tags []string) string {
+	return tags.join(',')
+}
+
+// publish sends an event to the Ntfy server with exponential backoff retry (3 attempts).
+pub fn (c NtfyClient) publish(event sources.Event) ! {
+	url := '${c.base_url}/${event.topic}'
+	mut header := http.Header{}
+	header.add_custom('Content-Type', 'text/plain')!
+	header.add_custom('X-Priority', event.priority.str())!
+	if event.tags.len > 0 {
+		header.add_custom('X-Tags', join_tags(event.tags))!
+	}
+	if c.auth_token != '' {
+		header.add(.authorization, 'Bearer ${c.auth_token}')
+	}
+
+	c.logger.debug('ntfy', 'publish',
+		'POST ${url} priority=${event.priority} tags=${join_tags(event.tags)}')
+
+	// Retry with exponential backoff: 3 attempts, 1s / 2s / 4s delays
+	mut last_err := error('unknown')
+	for attempt := 1; attempt <= 3; attempt++ {
+		resp := http.fetch(http.FetchConfig{
+			url:    url
+			method: .post
+			header: header
+			data:   event.message
+		}) or {
+			last_err = err
+			if attempt < 3 {
+				delay := time.second * (1 << (attempt - 1))
+				c.logger.warn('ntfy', 'publish',
+					'attempt ${attempt}/3 failed: ${err}, retrying in ${delay}')
+				time.sleep(delay)
+			}
+			continue
+		}
+
+		if resp.status_code >= 200 && resp.status_code < 300 {
+			c.logger.debug('ntfy', 'publish', 'success ${resp.status_code}')
+			return
+		}
+
+		last_err = error('ntfy returned ${resp.status_code}: ${resp.body}')
+		if attempt < 3 {
+			delay := time.second * (1 << (attempt - 1))
+			c.logger.warn('ntfy', 'publish',
+				'attempt ${attempt}/3 failed: ${last_err}, retrying in ${delay}')
+			time.sleep(delay)
+		}
+	}
+
+	return last_err
+}