Import DiscordChatExporter.Core.Exceptions and switch from a generic catch to catching DiscordChatExporterException only when it's non-fatal (catch (DiscordChatExporterException ex) when (!ex.IsFatal)). This ensures fatal exceptions propagate while non-fatal errors are counted and reported. Also clarified the channel option description by removing the incorrect 'in DMs' note about deletions.
Upstream replaced CliFx.Attributes with CliFx.Binding and now
requires command classes to be partial. Pipe() was also moved
from DiscordChatExporter.Core.Utils.Extensions to PowerKit.Extensions.
Introduce a message-deletion feature across CLI and GUI. Adds a new CLI command (deletemessages) with channel/before/after options and console progress. Extends DiscordClient with GetCurrentUserAsync and DeleteMessageAsync (including rate-limit handling) to perform deletions and surface authorization outcomes. GUI additions include DeleteSetup dialog, its ViewModel, view, and wiring: App registration, View/ViewModel managers, DashboardViewModel command, and a Delete button in the dashboard; deletion runs per-channel (parallel, with progress) and reports success/failure summaries.