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/application/conversation_service.rs

@@ -3,13 +3,6 @@
 //! `ConversationServiceImpl` is generic over `R: ConversationRepository`,
 //! delegating all persistence to that adapter.
 
-#![allow(
-    clippy::cast_possible_truncation,
-    clippy::cast_sign_loss,
-    clippy::cast_precision_loss,
-    clippy::cast_possible_wrap
-)]
-
 use anyhow::{Context, Result};
 
 use crate::domain::conversation::{ChatMessage, Conversation};