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.

config.v

@@ -0,0 +1,152 @@
+module main
+
+import os
+import yaml
+import sources
+
+pub struct ServerConfig {
+pub mut:
+	url         string @[json: 'url']
+	auth_token  string @[json: 'auth_token']
+	listen      string @[json: 'listen']
+	hmac_secret string @[json: 'hmac_secret'] // shared secret for webhook HMAC-SHA256 validation
+}
+
+pub struct DefaultConfig {
+pub mut:
+	priority int      @[json: 'priority']
+	tags     []string @[json: 'tags']
+}
+
+pub struct RateLimitConfig {
+pub mut:
+	max_per_minute int @[json: 'max_per_minute']
+	max_per_source int @[json: 'max_per_source']
+}
+
+pub struct DedupConfig {
+pub mut:
+	enabled     bool            @[json: 'enabled']
+	ttl_seconds int             @[json: 'ttl_seconds']
+	rate_limit  RateLimitConfig @[json: 'rate_limit']
+}
+
+pub struct SourcesConfig {
+pub mut:
+	gitea       []sources.GiteaSource      @[json: 'gitea']
+	uptime_kuma []sources.UptimeKumaSource @[json: 'uptime_kuma']
+	docker      []sources.DockerSource     @[json: 'docker']
+	http_poll   []sources.HttpPollSource   @[json: 'http_poll']
+	cron        []sources.CronSource       @[json: 'cron']
+	generic     []sources.GenericSource    @[json: 'generic']
+}
+
+pub struct Config {
+pub mut:
+	server   ServerConfig  @[json: 'server']
+	defaults DefaultConfig @[json: 'defaults']
+	sources  SourcesConfig @[json: 'sources']
+	dedup    DedupConfig   @[json: 'dedup']
+}
+
+pub fn load_config(path string) !Config {
+	if !os.exists(path) {
+		return error('config file not found: ${path}')
+	}
+	mut cfg := yaml.decode_file[Config](path)!
+
+	// Env override for auth token
+	env_token := os.getenv('NTFY_TOKEN')
+	if env_token != '' {
+		cfg.server.auth_token = env_token
+	}
+
+	// Env override for HMAC secret
+	env_hmac := os.getenv('NTFY_HMAC_SECRET')
+	if env_hmac != '' {
+		cfg.server.hmac_secret = env_hmac
+	}
+
+	validate_config(cfg)!
+	return cfg
+}
+
+pub fn validate_config(cfg Config) ! {
+	if cfg.server.url == '' {
+		return error('server.url is required')
+	}
+	if cfg.server.listen == '' {
+		return error('server.listen is required')
+	}
+	if cfg.defaults.priority < 1 || cfg.defaults.priority > 5 {
+		return error('defaults.priority must be between 1 and 5')
+	}
+
+	// Collect all webhook paths and detect duplicates
+	mut seen_paths := map[string]string{} // path -> source description
+
+	for src in cfg.sources.gitea {
+		if src.webhook_path == '' {
+			return error('gitea source "${src.name}" missing webhook_path')
+		}
+		if src.topic == '' {
+			return error('gitea source "${src.name}" missing topic')
+		}
+		check_duplicate_path(mut seen_paths, src.webhook_path, 'gitea:${src.name}')!
+	}
+	for src in cfg.sources.uptime_kuma {
+		if src.webhook_path == '' {
+			return error('uptime_kuma source "${src.name}" missing webhook_path')
+		}
+		if src.topic == '' {
+			return error('uptime_kuma source "${src.name}" missing topic')
+		}
+		check_duplicate_path(mut seen_paths, src.webhook_path, 'uptime_kuma:${src.name}')!
+	}
+	for src in cfg.sources.docker {
+		if src.topic == '' {
+			return error('docker source "${src.name}" missing topic')
+		}
+		if src.hosts.len == 0 {
+			return error('docker source "${src.name}" requires at least one host')
+		}
+	}
+	for src in cfg.sources.http_poll {
+		if src.interval <= 0 {
+			return error('http_poll source "${src.name}" interval must be > 0')
+		}
+		for chk in src.checks {
+			if chk.url == '' {
+				return error('http_poll check missing url')
+			}
+			if chk.topic == '' {
+				return error('http_poll check for "${chk.url}" missing topic')
+			}
+		}
+	}
+	for src in cfg.sources.cron {
+		if src.webhook_path == '' {
+			return error('cron source "${src.name}" missing webhook_path')
+		}
+		if src.topic == '' {
+			return error('cron source "${src.name}" missing topic')
+		}
+		check_duplicate_path(mut seen_paths, src.webhook_path, 'cron:${src.name}')!
+	}
+	for src in cfg.sources.generic {
+		if src.webhook_path == '' {
+			return error('generic source "${src.name}" missing webhook_path')
+		}
+		if src.topic == '' {
+			return error('generic source "${src.name}" missing topic')
+		}
+		check_duplicate_path(mut seen_paths, src.webhook_path, 'generic:${src.name}')!
+	}
+}
+
+fn check_duplicate_path(mut seen map[string]string, path string, source_name string) ! {
+	if existing := seen[path] {
+		return error('duplicate webhook path "${path}" used by ${existing} and ${source_name}')
+	}
+	seen[path] = source_name
+}