add: live encode progress tracking and read-only status web UI

Stream ffmpeg -progress during the video encode into an in-memory tracker
(internal/status) so the long-running step is no longer a black box: percent,
fps, speed, and ETA are derived from the source duration and updated ~1/s.
Progress prints to stdout only (no logs.db row) to avoid burying real events.

Expose it over HTTP (internal/server, default :8080, set http_addr to "" to
disable): GET /status returns the live snapshot, the pending input queue, and
recent non-debug events; GET / serves an embedded dashboard that polls /status
every second. The server shuts down on the same SIGINT/SIGTERM context as the
watcher.

pkg/types/types.go

@@ -34,8 +34,11 @@ type Metadata struct {
 type Config struct {
 	OMDBAPIKey       string `yaml:"omdb_api_key"`
 	LogRetentionDays int    `yaml:"log_retention_days"`
-	Encoding         EncodingConfig
-	Paths            PathsConfig
+	// HTTPAddr is the status server listen address. Absent (nil) defaults to
+	// ":8080"; an explicit empty string disables the server.
+	HTTPAddr *string `yaml:"http_addr"`
+	Encoding EncodingConfig
+	Paths    PathsConfig
 }
 
 type EncodingConfig struct {