Select the installed language pack when launching MoonWell

Pass WOW_LOCALE=auto alongside the selected Data directory so inherited locale
settings cannot override an installed ruRU pack. Keep language archives in the
regular manifest download and verification flow. Document the contract and
prepare launcher version 1.0.7+10 for the localization release.

Verified on Windows through FVM: full format check and flutter analyze passed;
all 76 Flutter tests passed, including manifest retention and verification of
Russian archives and the game's child environment. No macOS build was run.

README.md

@@ -73,6 +73,12 @@ folder. For builds that pin an endpoint, set
 `--dart-define=MOONWELL_AUTH_ADDRESS=login.example:3724` instead. This endpoint is
 the vMaNGOS auth server, separate from the realm's world port and the Web API.
 
+Russian 1.12.1 language archives are regular manifest files under `Data/ruRU`
+(or `WoW/Data/ruRU` for a nested install). They are downloaded and verified with
+the same size and SHA-256 checks as the base client. The launcher passes
+`WOW_LOCALE=auto` to the game: an installed pack selects Russian, and a base-only
+install selects English, regardless of the launcher's inherited environment.
+
 Example run command:
 
 ```powershell