Log files source: follow the logs of Traefik, nginx and other programs

Files source (source_type=file), declared in Settings > Log sources > Log
files (/data/files.json, 50 at most): name (= app), path as mounted in the
container (file or glob, rotated copies .1/.gz left out, 200 files per
glob), format, optional host, switch.

- formats: plain text (level detected, leading timestamp read and removed),
  JSON lines (msg/time/level keys, numeric pino levels, other keys as
  fields, nested ones dotted), logfmt, access log CLF (nginx, Apache,
  Traefik CLF with router/backend/duration), Traefik access log in JSON
  (summary "GET host/path 200 · 12.5 ms · router · client"), regular
  expression with named groups time/level/msg/host/app/status; 5xx = err,
  4xx = warning; fields named like LogStream's own renamed field_<name>
- indented lines (text) and non-matching lines (regex) added to the
  previous entry, which waits 2 s for them
- inode + offset per file in /data/files-state.json, rotation (end of
  .1 read first), copytruncate, file renamed within the glob; last
  FILES_BACKFILL (1h) of dated lines read when turned on, new files read
  from their start
- status per file (files followed, entries read, not found / permission)

UI: rows with switch, name, path, format, host (regex field when needed),
status line; green edge, tint and FILE badge in the list, "Files" in the
source filter, HTTP fields first in the details, FR/EN. docker-compose,
.env.example and README (EN/FR): mounts, formats, FILES_BACKFILL.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

main.go

@@ -43,6 +43,7 @@ type config struct {
 	auditLog   string
 	auditHost  string
 	auditFill  time.Duration
+	filesFill  time.Duration
 	batchSize  int
 	queueSize  int
 	flushEvery time.Duration
@@ -125,6 +126,7 @@ func main() {
 		auditLog:   getenv("AUDIT_LOG", "/var/log/audit/audit.log"),
 		auditHost:  os.Getenv("AUDIT_HOST"),
 		auditFill:  getenvDuration("AUDIT_BACKFILL", time.Hour),
+		filesFill:  getenvDuration("FILES_BACKFILL", time.Hour),
 		batchSize:  getenvInt("BATCH_SIZE", 1000),
 		queueSize:  getenvInt("QUEUE_SIZE", 100000),
 		flushEvery: time.Duration(getenvInt("FLUSH_MS", 1000)) * time.Millisecond,
@@ -218,6 +220,10 @@ func main() {
 	// Linux audit log of the host (auditd), off until enabled in Settings > Sources.
 	api.audit = NewAudit(cfg.auditLog, cfg.hostRoot, cfg.auditHost, cfg.dataDir, cfg.auditFill, sink)
 	go api.audit.Run(ctx)
+	// Log files of other programs (Traefik, nginx…) mounted in the container,
+	// declared in Settings > Sources.
+	api.files = NewFiles(cfg.hostRoot, cfg.dataDir, cfg.filesFill, sink)
+	go api.files.Run(ctx)
 	api.selfLog = selfLog
 	api.Routes(mux)
 	mux.Handle("GET /", http.FileServer(http.FS(static)))