refactor: consolidate #![allow(clippy::cast_*)] to crate roots

Add the cast-allow block to zesdex-entities/src/lib.rs and
zesdex-utils/src/lib.rs (which lacked it), then remove from
65 sub-files across all 8 crates. Build and all 223 tests
continue to pass.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/zesdex-cms/src/domain/service.rs

@@ -3,13 +3,6 @@
 //! These traits are implemented by the application layer and consumed by
 //! infrastructure adapters (HTTP handlers, CLI commands, etc.).
 
-#![allow(
-    clippy::cast_possible_truncation,
-    clippy::cast_sign_loss,
-    clippy::cast_precision_loss,
-    clippy::cast_possible_wrap
-)]
-
 use anyhow::Result;
 
 use super::conversation::{ChatMessage, Conversation};