feat(notifications): add Bark push support

Add Bark as a supported Apprise notification protocol.

Supported URL formats:
- bark://bark_key uses the official Bark server at https://api.day.app/
- bark://host/bark_key uses a custom Bark server over HTTP
- barks://host/bark_key uses a custom Bark server over HTTPS

Bark notifications are sent with POST JSON payloads containing the device key, title, and body. The notification settings modal now
lists Bark examples in the Apprise URL placeholder and support text.

src/routes/settings/notifications/NotificationModal.svelte

@@ -427,11 +427,14 @@ ntfy://host/topic?auth=base64token&priority=3
 ntfys://host/topic?auth=base64token
 pushover://user_key/api_token
 workflows://hostname/workflow/signature
+bark://bark_key
+bark://host/bark_key
+barks://host/bark_key
 jsons://hostname/webhook/path"
 						class="flex min-h-[220px] w-full rounded-md border border-input bg-transparent px-3 py-2 text-sm shadow-sm placeholder:text-muted-foreground focus-visible:outline-none focus-visible:ring-1 focus-visible:ring-ring"
 					></textarea>
 					<p class="text-xs text-muted-foreground">
-						Supports Gotify (gotify:// or gotifys:// for HTTPS), Discord, Slack, Mattermost (mmost:// or mmosts://), Telegram, ntfy, Pushover, Workflows (for e.g. Microsoft Teams), and generic JSON webhooks.
+						Supports Gotify (gotify:// or gotifys:// for HTTPS), Discord, Slack, Mattermost (mmost:// or mmosts://), Telegram, ntfy, Bark, Pushover, Workflows (for e.g. Microsoft Teams), and generic JSON webhooks.
 						</p>
 					</div>
 				</div>