Postbox -> TelegramEngine waves 11-14: stateManager collapse + BUILD-dep sweep

Wave 11: ActionSheetPeerItem de-Postboxed. Revisits wave-1 abandonment.
`postbox: Postbox, network: Network` init params collapse to
`stateManager: AccountStateManager`; avatar setPeer call routes via
`item.stateManager.postbox` / `.network`. Module never names Postbox.
Sole caller (ShareController.swift:1146) migrated in place.

Wave 12: HorizontalPeerItem de-Postboxed (same pattern). Ripples the
collapse up into ChatListSearchRecentPeersNode's public init
(`postbox:/network:` -> `stateManager:`). That module still imports
Postbox for PostboxViewKey/UnreadMessageCountsView internals but its
public surface simplifies. 3 external caller sites migrated.

Wave 13: AttachmentTextInputPanelNode minor cleanup. Module was already
Postbox-free at source level (wave 6) but carried a dead BUILD dep and
had 2 raw `peerId?.namespace == Namespaces.Peer.SecretChat` checks.
Both now use existing `PeerId.isSecretChat` extension in TelegramCore.

Wave 14: BUILD-dep sweep mirroring wave 6's source sweep. 98 modules
had `//submodules/Postbox:Postbox` (or `//submodules/Postbox`) BUILD
deps despite no source file importing Postbox since wave 6. Single
iteration, zero restores -- Bazel Swift requires source-level `import`
for symbol resolution, so redundant BUILD deps are pure metadata.

Net: 110 files, +116/-149. Build verified green (debug_sim_arm64).

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

submodules/PeerAvatarGalleryUI/BUILD

@@ -13,7 +13,6 @@ swift_library(
         "//submodules/SSignalKit/SwiftSignalKit:SwiftSignalKit",
         "//submodules/AsyncDisplayKit:AsyncDisplayKit",
         "//submodules/Display:Display",
-        "//submodules/Postbox:Postbox",
         "//submodules/TelegramCore:TelegramCore",
     	"//submodules/TelegramPresentationData:TelegramPresentationData",
         "//submodules/AccountContext:AccountContext",