Refactor SQL queries into a dedicated module

- Moved SQL queries from multiple worker files into `src/worker/sql.rs` for better organization and maintainability.
- Updated references in `stockage_manager.rs`, `transport.rs`, `underground.rs`, `user_character.rs`, and `value_recalculation.rs` to use the new centralized SQL queries.
- Improved code readability by replacing `.get(0)` with `.first()` for better clarity when retrieving the first row from query results.
- Cleaned up unnecessary comments and consolidated related SQL queries.

src/websocket_server.rs

@@ -86,15 +86,7 @@ async fn append_ws_log(
             .map(|s| s.to_string());
         let target_user = json
             .get("user_id")
-            .and_then(|v| {
-                if let Some(s) = v.as_str() {
-                    Some(s.to_string())
-                } else if let Some(n) = v.as_i64() {
-                    Some(n.to_string())
-                } else {
-                    None
-                }
-            });
+            .and_then(|v| v.as_str().map(|s| s.to_string()).or_else(|| v.as_i64().map(|n| n.to_string())));
         (event, target_user)
     } else {
         (None, None)
@@ -510,10 +502,8 @@ async fn handle_connection<S>(
                                         .and_then(|v| {
                                             if let Some(s) = v.as_str() {
                                                 s.parse::<i64>().ok()
-                                            } else if let Some(n) = v.as_i64() {
-                                                Some(n)
                                             } else {
-                                                None
+                                                v.as_i64()
                                             }
                                         })
                                         .map(|v| v == numeric_uid)