Revert "Add Anki Sync Server addon (self-hosted flashcard sync)"

This reverts commit 75baab8914.

install.sh

@@ -37,10 +37,7 @@
 #     Display/Lockout, the webui/ Node app installed as a systemd
 #     service; no login of its own, put it behind your own reverse proxy
 #     with Authelia forward-auth if it needs to be reachable beyond a
-#     trusted LAN - see the file header), Anki Sync Server
-#     (menus/addon_anki_sync.sh - self-hosted flashcard sync via the
-#     official `python -m anki.syncserver`, for Anki desktop/AnkiDroid
-#     clients on the LAN instead of AnkiWeb).
+#     trusted LAN - see the file header).
 #   Advanced: Diagnostics (menus/diagnostics.sh - system status/logs/
 #     audio/network), Electron Maintenance (menus/advanced_electron.sh -
 #     manual update, fix blank screen), Factory Reset
@@ -97,8 +94,6 @@ source "$SCRIPT_DIR/menus/addon_lms_squeezelite.sh"
 source "$SCRIPT_DIR/menus/addon_asterisk_intercom.sh"
 # shellcheck source=menus/addon_webui.sh
 source "$SCRIPT_DIR/menus/addon_webui.sh"
-# shellcheck source=menus/addon_anki_sync.sh
-source "$SCRIPT_DIR/menus/addon_anki_sync.sh"
 # shellcheck source=menus/advanced_electron.sh
 source "$SCRIPT_DIR/menus/advanced_electron.sh"
 # shellcheck source=menus/advanced_upgrade.sh
@@ -179,8 +174,8 @@ core_settings_menu() {
 }
 
 addons_menu_builder() {
-    MENU_LABELS=("CUPS Printing" "Authelia Auto-Login" "Remote Access" "LMS Server / Squeezelite Player" "Asterisk Intercom (SIP Extension)" "Web UI" "Anki Sync Server")
-    MENU_HANDLERS=(addon_cups_menu addon_authelia_menu remote_access_menu addon_lms_squeezelite_menu addon_asterisk_intercom_menu addon_webui_menu addon_anki_sync_menu)
+    MENU_LABELS=("CUPS Printing" "Authelia Auto-Login" "Remote Access" "LMS Server / Squeezelite Player" "Asterisk Intercom (SIP Extension)" "Web UI")
+    MENU_HANDLERS=(addon_cups_menu addon_authelia_menu remote_access_menu addon_lms_squeezelite_menu addon_asterisk_intercom_menu addon_webui_menu)
 }
 
 addons_menu() {