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>

docker-compose.yml

@@ -39,6 +39,7 @@ services:
       HOST_LOGS_BACKFILL: ${HOST_LOGS_BACKFILL:-1h}   # historique lu a l'activation des logs systeme de l'hote
       DMESG_BACKFILL: ${DMESG_BACKFILL:-1h}   # historique lu a l'activation des messages du noyau (dmesg)
       AUDIT_BACKFILL: ${AUDIT_BACKFILL:-1h}   # historique lu a l'activation de l'audit Linux (auditd)
+      FILES_BACKFILL: ${FILES_BACKFILL:-1h}   # historique lu a l'activation d'un fichier de logs (Reglages > Sources)
       AUDIT_HOST: ${AUDIT_HOST:-}             # nom d'hote des evenements d'audit (vide : node= des enregistrements, sinon /host/etc/hostname)
     group_add:
       - "${HOST_LOGS_GID:-4}"        # groupe autorise a lire les logs de l'hote (4 = adm sur Debian/Ubuntu)
@@ -63,6 +64,8 @@ services:
       # noms des utilisateurs et de l'hote pour les evenements d'audit (optionnel)
       # - /etc/passwd:/host/etc/passwd:ro
       # - /etc/hostname:/host/etc/hostname:ro
+      # fichiers de logs d'autres programmes (Traefik, nginx...), a declarer dans Reglages > Sources > Fichiers de logs
+      # - /var/log/traefik:/logs/traefik:ro
       # logo de la page de connexion, avec LOGIN_LOGO=/config/logo.png dans .env
       # - ./logo.png:/config/logo.png:ro
       # prereglages de tags personnalises, avec PRESETS_FILE=/config/presets.json dans .env