feat: consolidate WiFi/MQTT/FTP/Bluetooth into a Settings tab with sub-tabs

Merge the WiFi, MQTT, FTP and Bluetooth settings together with the general
settings into a single top-level "Settings" tab, presented UniFi-style with
centered horizontal sub-tabs (General / Buttons / WiFi / MQTT / FTP /
Bluetooth) directly beneath the top tabs. The button-assignment config moves
into its own "Buttons" sub-tab; the Help tab is removed and the General tab
buttons/options compacted. Adds an FTP start/stop button to the control tab.

Also fixes three issues found while testing on the device:
- Sleep-timer dropdown stayed open on outside-click because the ~1s Pong-driven
  updateSleepTimerState() reassigned the toggle's full className, clobbering
  Bootstrap's `show` class. Now toggles only `active-magenta` via classList.
- Desktop control-tab volume slider rendered at zero width: the bootstrap-slider
  is created while the control tab is hidden (default landing tab is Files), so
  it is now relayout()'d on shown.bs.tab.
- RFID reader-type help text referenced a missing i18n key
  (general.rfid.readerType.description) -> corrected to general.rfid.description.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: fhirschmann

html/locales/de.json

@@ -36,6 +36,8 @@
 		"ftp": "FTP",
 		"bluetooth": "Bluetooth",
 		"general": "Allgemein",
+		"settings": "Einstellungen",
+		"buttons": "Tasten",
 		"tools": "Tools",
 		"help": "Hilfe"
 	},
@@ -168,6 +170,8 @@
 		"btHeadphones": "Kopfhörer",
 		"nightOn": "Nacht An",
 		"nightOff": "Nacht Aus",
+		"ftpOn": "FTP An",
+		"ftpOff": "FTP Aus",
 		"repeatOff": "Aus",
 		"repeatPlaylist": "Playlist",
 		"repeatTrack": "Titel",

html/locales/en.json

@@ -36,6 +36,8 @@
 		"ftp": "FTP",
 		"bluetooth": "Bluetooth",
 		"general": "General",
+		"settings": "Settings",
+		"buttons": "Buttons",
 		"tools": "Tools",
 		"help": "Help"
 	},
@@ -169,6 +171,8 @@
 		"btHeadphones": "Headphones",
 		"nightOn": "Night On",
 		"nightOff": "Night Off",
+		"ftpOn": "FTP On",
+		"ftpOff": "FTP Off",
 		"repeatOff": "Off",
 		"repeatPlaylist": "Playlist",
 		"repeatTrack": "Track",

html/locales/fr.json

@@ -36,6 +36,8 @@
 		"ftp": "FTP",
 		"bluetooth": "Bluetooth",
 		"general": "Général",
+		"settings": "Paramètres",
+		"buttons": "Boutons",
 		"tools": "Outils",
 		"help": "Aide"
 	},
@@ -161,6 +163,8 @@
 		"btHeadphones": "Casque",
 		"nightOn": "Nuit On",
 		"nightOff": "Nuit Off",
+		"ftpOn": "FTP On",
+		"ftpOff": "FTP Off",
 		"repeatOff": "Off",
 		"repeatPlaylist": "Playlist",
 		"repeatTrack": "Piste",