Šepot — end-to-end encrypted messenger

Initial public release. Anonymous on-device identity (no phone number,
e-mail, or password), Signal-protocol cryptography (X3DH + PQXDH, Double
Ratchet, sealed sender) via libsignal, a metadata-minimizing relay,
group chats, disappearing messages, encrypted local storage, optional
Tor transport, and a UI localized into Czech, English, German, Russian,
and Italian.

Monorepo: Flutter client (app/), Rust relay + wire types (rust/),
protobuf definitions (proto/), self-host deploy (deploy/).

Licensed under AGPL-3.0 with an app-store distribution exception (§7).

app/test/identity_recover_test.dart

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+import 'dart:typed_data';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:sepot/core/crypto/mnemonic.dart';
+
+// Obnova účtu stojí na reverzibilitě mnemonicu: 24 slov -> týž privátní
+// klíč. Plnou identitu (LocalIdentity.create/recover) nejde testovat v čistém
+// Dart VM — libsignal je native. Tady ověřujeme to podstatné bez native.
+void main() {
+  test('mnemonic round-trip je stabilní (základ obnovy účtu)', () {
+    final key = Uint8List.fromList(List.generate(32, (i) => (i * 7 + 3) & 0xff));
+    final words = SepotMnemonic.encode(key);
+    expect(words.length, 24);
+    expect(SepotMnemonic.isValid(words), isTrue);
+
+    final decoded = SepotMnemonic.decode(words);
+    // deserialize -> serialize stabilní: obnova vždy vrátí identická slova/klíč
+    expect(SepotMnemonic.encode(decoded), words);
+    expect(SepotMnemonic.decode(SepotMnemonic.encode(decoded)), decoded);
+  });
+
+  test('neplatná fráze se pozná', () {
+    final words = SepotMnemonic.encode(Uint8List.fromList(List.filled(32, 0x11)));
+    expect(SepotMnemonic.isValid(words.sublist(0, 23)), isFalse); // málo slov
+    final broken = [...words]..[0] = 'zzzzzz';
+    expect(SepotMnemonic.isValid(broken), isFalse); // neznámé slovo
+  });
+}