Postbox refactor waves 278-356: squash

Squashes 79 sequential refactor waves into a single commit.

Highlights:
- Drop `import Postbox` (and matching `//submodules/Postbox` BUILD deps) from a wide swath of consumer files: ChatList, ChatMessage*BubbleContentNode subclasses, ListMessageNode/ListMessageItem, GalleryData, ChatHistorySearchContainerNode, ChatPanelInterfaceInteraction, ChatControllerInteraction, ChatMessageStickerItemNode, ChatMessageReplyInfoNode, ChatMessageInstantVideoItemNode, ChatPresentationInterfaceState, BrowserMarkdown/Readability, MediaResources, LocalMediaResources, ICloudResources, FetchManager, ShareController, OpenChatMessage, GalleryController, GroupStickerSearchContainerNode, GroupStickerPackCurrentItem, ChatPinnedMessageTitlePanelNode, OverlayAudioPlayerController, PresentationThemeSettings, StatisticsUI/StoryIconNode, TextFormat/StringWithAppliedEntities, GalleryUI/VideoAdComponent, StickerPackPreviewUI, WallpaperPreviewMedia, WallpaperResources, YoutubeEmbedImplementation, InstantPageExternalMediaResource, PlatformRestrictionMatching, TelegramUIDeclareEncodables, ChatListNode/ChatListSearchContainerNode.
- Add `TelegramEngine` facades: `Themes.wallpapers`, `Themes.themes`, `AccountData.addAppLogEvent`.
- Add `EngineMessageHistoryEntryLocation` wrapper.
- Add `EngineRaw*` escape-hatch typealiases (`EngineRawMessage`, `EngineRawPeer`, `EngineRawMedia`, `EngineRawMediaResource`, `EngineRawMediaResourceData`, `EngineRawItemCollectionItem`, `EngineRawItemCollectionInfo`) and `engineDeclareEncodable` forwarder.
- Drop unused `account:`/`postbox:`/`network:` parameters from several public functions and delete the dead overloads/types/functions left over: `automaticThemeShouldSwitchNow`, `cancelFreeMediaFileInteractiveFetch`, `legacyEnqueueVideoMessage`, `TelegramMediaFileReference`, plus assorted dead public TelegramCore/AccountContext SecureId entry points.
- Delete entire dead modules: `LegacyDataImport`, `TonBinding`, `SpotlightSupport`, `SvgRendering`, third-party `AppCenter`/`VectorPlus`/`SwiftColor`/`SwiftSVG`.
- Drop orphan `//submodules/Postbox` BUILD deps across 3 cleanup rounds.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

submodules/TelegramCallsUI/Sources/LegacyCallControllerNode.swift

@@ -2,7 +2,6 @@ import Foundation
 import UIKit
 import Display
 import AsyncDisplayKit
-import Postbox
 import TelegramCore
 import SwiftSignalKit
 import TelegramPresentationData