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>

web/index.html

@@ -193,28 +193,6 @@
                   <button id="addTag" class="btn primary" type="button" data-i18n="addTag">+ Add tag</button>
                   <select id="presetTags" class="field" aria-label="Presets" data-i18n-aria="presetAria">
                     <option value="" data-i18n="presetPick">+ Preset…</option>
-                    <optgroup label="HTTP/HTTPS">
-                      <option value="http_status" data-i18n="preset_http_status">HTTP status codes</option>
-                      <option value="http_methods" data-i18n="preset_http_methods">HTTP methods</option>
-                      <option value="http_probes" data-i18n="preset_http_probes">Probes and attacks</option>
-                      <option value="http_bots" data-i18n="preset_http_bots">Bots and scripts</option>
-                      <option value="http_errors" data-i18n="preset_http_errors">TLS/HTTPS and proxy errors</option>
-                    </optgroup>
-                    <optgroup label="System" data-i18n-label="presetGroupSys">
-                      <option value="sys_auth" data-i18n="preset_sys_auth">SSH and logins</option>
-                      <option value="sys_sudo" data-i18n="preset_sys_sudo">sudo commands</option>
-                      <option value="sys_kernel" data-i18n="preset_sys_kernel">Kernel: OOM, crashes, disks</option>
-                      <option value="sys_systemd" data-i18n="preset_sys_systemd">systemd services</option>
-                      <option value="sys_firewall" data-i18n="preset_sys_firewall">Firewall and fail2ban</option>
-                    </optgroup>
-                    <optgroup label="Applications" data-i18n-label="presetGroupApps">
-                      <option value="app_docker" data-i18n="preset_app_docker">Docker and containers</option>
-                      <option value="app_db" data-i18n="preset_app_db">Databases</option>
-                    </optgroup>
-                    <optgroup label="General" data-i18n-label="presetGroupGen">
-                      <option value="gen_levels" data-i18n="preset_gen_levels">Log levels</option>
-                      <option value="gen_ip" data-i18n="preset_gen_ip">IPv4 addresses</option>
-                    </optgroup>
                   </select>
                 </span>
                 <button id="resetTags" class="btn ghost" type="button" data-i18n="resetTags">Restore default tags</button>