docs(readme): correct fork-sync version (v4.12.3) and logo path

Two stale facts in README.md: it said "Forked from Cinny v4.12.1" (we've since
synced through v4.12.3) and referenced the logo as lotus_chat.png (the file is
public/res/Lotus.png). CONTRIBUTING.md is intentionally left as upstream
Cinny's and is not modified.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

@@ -2,7 +2,7 @@
 
 A Matrix chat client built for Lotus Guild — fast, private, and packed with the features you actually want.
 
-**Deployed at [chat.lotusguild.org](https://chat.lotusguild.org)**  |  Forked from [Cinny](https://github.com/cinnyapp/cinny) v4.12.1
+**Deployed at [chat.lotusguild.org](https://chat.lotusguild.org)**  |  Forked from [Cinny](https://github.com/cinnyapp/cinny), synced through v4.12.3
 
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@@ -10,7 +10,7 @@ A Matrix chat client built for Lotus Guild — fast, private, and packed with th
 
 The source code is licensed under [AGPLv3](LICENSE), the same license as the upstream Cinny project. The source for this fork is public at [code.lotusguild.org/LotusGuild/cinny](https://code.lotusguild.org/LotusGuild/cinny).
 
-The Lotus Chat logo (`lotus_chat.png`) is a derivative work based on the original Cinny logo by Ajay Bura and contributors, used under [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/). The modified logo is © Lotus Guild and is also made available under CC BY 4.0.
+The Lotus Chat logo (`public/res/Lotus.png`) is a derivative work based on the original Cinny logo by Ajay Bura and contributors, used under [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/). The modified logo is © Lotus Guild and is also made available under CC BY 4.0.
 
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