feat(master): POLL_INTERVAL, poller wiring and version picker in the UI (#9)

internal/master/config/config.go

@@ -28,11 +28,17 @@ type Config struct {
 	// UpdateTimeout bounds how long one webhook request waits for its auto
 	// jobs (UPDATE_TIMEOUT, default 5m).
 	UpdateTimeout time.Duration
+	// PollInterval is the time between registry polling cycles
+	// (POLL_INTERVAL, default 6h).
+	PollInterval time.Duration
 }
 
 // defaultUpdateTimeout is used when UPDATE_TIMEOUT is unset.
 const defaultUpdateTimeout = 5 * time.Minute
 
+// defaultPollInterval is used when POLL_INTERVAL is unset.
+const defaultPollInterval = 6 * time.Hour
+
 // Load reads and validates the master configuration, failing fast on
 // anything missing so a half-configured master never starts.
 func Load() (*Config, error) {
@@ -50,6 +56,7 @@ func Load() (*Config, error) {
 		LogLevel:         getenvDefault("LOG_LEVEL", "info"),
 		UpdaterAPIKey:    os.Getenv("UPDATER_API_KEY"),
 		UpdateTimeout:    defaultUpdateTimeout,
+		PollInterval:     defaultPollInterval,
 	}
 	for _, r := range []struct{ name, value string }{
 		{"DATABASE_URL", cfg.DatabaseURL},
@@ -77,6 +84,13 @@ func Load() (*Config, error) {
 		}
 		cfg.UpdateTimeout = d
 	}
+	if v := os.Getenv("POLL_INTERVAL"); v != "" {
+		d, err := time.ParseDuration(v)
+		if err != nil || d <= 0 {
+			return nil, fmt.Errorf("POLL_INTERVAL must be a positive duration such as 6h, got %q", v)
+		}
+		cfg.PollInterval = d
+	}
 	return cfg, nil
 }