v0.6.0: healthcheck + hub reporting implementation

- Add heartbeat ping (every 5 min, controller alive signal)
- Add backup integrity check (weekly restic check, Sunday 04:00)
- Add Heartbeat + BackupIntegrity fields to PingUUIDsConfig
- Add HubConfig for central hub reporting
- Add report package (types, builder, pusher) for hub push
- Wire hub reporting into scheduler (configurable interval)
- Update controller.yaml.example with new monitoring + hub sections
- Add monitoring/DEPRECATED.md for legacy bash scripts

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

controller/internal/config/config.go

@@ -20,6 +20,7 @@ type Config struct {
 	Stacks         StacksConfig         `yaml:"stacks"`
 	Backup         BackupConfig         `yaml:"backup"`
 	Monitoring     MonitoringConfig     `yaml:"monitoring"`
+	Hub            HubConfig            `yaml:"hub"`
 	SelfUpdate     SelfUpdateConfig     `yaml:"self_update"`
 	Notifications  NotificationsConfig  `yaml:"notifications"`
 	Logging        LoggingConfig        `yaml:"logging"`
@@ -98,9 +99,11 @@ type MonitoringConfig struct {
 }
 
 type PingUUIDsConfig struct {
-	DBDump       string `yaml:"db_dump"`
-	Backup       string `yaml:"backup"`
-	SystemHealth string `yaml:"system_health"`
+	Heartbeat       string `yaml:"heartbeat"`
+	DBDump          string `yaml:"db_dump"`
+	Backup          string `yaml:"backup"`
+	SystemHealth    string `yaml:"system_health"`
+	BackupIntegrity string `yaml:"backup_integrity"`
 }
 
 type ThresholdsConfig struct {
@@ -136,6 +139,13 @@ type AssetsConfig struct {
 	SourceURL string `yaml:"source_url"` // Only used during build, not runtime
 }
 
+type HubConfig struct {
+	Enabled      bool   `yaml:"enabled"`
+	URL          string `yaml:"url"`
+	APIKey       string `yaml:"api_key"`
+	PushInterval string `yaml:"push_interval"`
+}
+
 // Load reads and parses the config file, applies defaults, and validates.
 func Load(path string) (*Config, error) {
 	data, err := os.ReadFile(path)
@@ -198,6 +208,7 @@ func applyDefaults(cfg *Config) {
 	di(&cfg.Monitoring.Thresholds.CPUWarnPercent, 90)
 	di(&cfg.Monitoring.Thresholds.MemoryWarnPercent, 85)
 	di(&cfg.Monitoring.Thresholds.TemperatureWarnCelsius, 75)
+	d(&cfg.Hub.PushInterval, "15m")
 	d(&cfg.SelfUpdate.CheckInterval, "6h")
 	di(&cfg.SelfUpdate.HealthTimeoutSeconds, 60)
 	d(&cfg.Logging.Level, "info")