fix(app): make composer input IME-safe and paste-aware (#3343)

* fix(app): preserve native composer input semantics

Native text was round-tripped through application state on every keystroke, which could overwrite an input method's in-flight edits. Keep native text ownership inside the input and reserve application-driven replacement for explicit draft mutations.\n\nRoute native clipboard images through the existing persisted attachment pipeline so keyboard and system paste actions behave like other image sources.

* fix(nix): refresh dependency hash

The native composer dependency changes the fixed npm dependency closure used by desktop builds.

* fix(app): keep composer locked across image pastes

Count concurrent native image persistence operations so submit remains disabled until every pasted image is attached.

* fix(app): replace composer text through the DOM on web

Web TextInput refs are DOM elements, so application-driven draft replacement must update their value and selection without native setNativeProps.

* fix(app): preserve web IME composition

Carry the Chinese IME fix from #2990 into the web composer input boundary.

Co-authored-by: Jimmy Lee <jimersylee+github@gmail.com>

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Co-authored-by: Jimmy Lee <jimersylee+github@gmail.com>

packages/app/package.json

@@ -48,6 +48,7 @@
     "@getpaseo/protocol": "*",
     "@gorhom/bottom-sheet": "^5.2.14",
     "@gorhom/portal": "^1.0.14",
+    "@mattermost/react-native-paste-input": "2.0.1",
     "@react-native-async-storage/async-storage": "2.2.0",
     "@react-native-masked-view/masked-view": "^0.3.2",
     "@react-native/normalize-colors": "^0.81.5",