Load color tag presets from an editable presets.json file

The presets move from app.js to presets.json, built into the binary and
served by /api/presets. PRESETS_FILE (default /data/presets.json) replaces
the list when present; it is read again each time Settings opens and the
built-in list is used if it is invalid. docs/presets.md (EN/FR) explains
each preset and the file format.

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

.env.example

@@ -12,6 +12,11 @@ AUTH_PASS=
 # local mode: PNG logo shown on the login page, path inside the container (empty = no logo).
 # Mount the file in docker-compose.yml, e.g. ./logo.png:/config/logo.png:ro, then LOGIN_LOGO=/config/logo.png
 LOGIN_LOGO=
+
+# Ready-made color tags offered in Settings > Filters (see docs/presets.md).
+# Empty: /data/presets.json if present, else the built-in list. To use your own file,
+# mount it in docker-compose.yml, e.g. ./presets.json:/config/presets.json:ro
+PRESETS_FILE=
 # Session lifetime, both modes (e.g. 8h, 24h)
 SESSION_TTL=12h
 # oidc mode: issuer URL exactly as the provider announces it