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/worker/stockage_manager.rs

@@ -8,49 +8,17 @@ use std::sync::Arc;
 use std::time::{Duration, Instant};
 
 use super::base::{BaseWorker, Worker, WorkerState};
+use crate::worker::sql::{
+    QUERY_GET_TOWNS,
+    QUERY_INSERT_STOCK,
+    QUERY_CLEANUP_STOCK,
+    QUERY_GET_REGION_USERS,
+};
 
 pub struct StockageManager {
     base: BaseWorker,
 }
 
-// SQL-Queries analog zu `stockagemanager.h`
-const QUERY_GET_TOWNS: &str = r#"
-    SELECT fdr.id
-      FROM falukant_data.region fdr
-      JOIN falukant_type.region ftr
-        ON ftr.id = fdr.region_type_id
-     WHERE ftr.label_tr = 'city';
-"#;
-
-const QUERY_INSERT_STOCK: &str = r#"
-    INSERT INTO falukant_data.buyable_stock (region_id, stock_type_id, quantity)
-    SELECT
-        $1 AS region_id,
-        s.id AS stock_type_id,
-        GREATEST(1, ROUND(RANDOM() * 5 * COUNT(br.id))) AS quantity
-      FROM falukant_data.branch AS br
-      CROSS JOIN falukant_type.stock AS s
-     WHERE br.region_id = $1
-     GROUP BY s.id
-     ORDER BY RANDOM()
-     LIMIT GREATEST(
-         ROUND(RANDOM() * (SELECT COUNT(id) FROM falukant_type.stock)),
-         1
-     );
-"#;
-
-const QUERY_CLEANUP_STOCK: &str = r#"
-    DELETE FROM falukant_data.buyable_stock
-     WHERE quantity <= 0;
-"#;
-
-const QUERY_GET_REGION_USERS: &str = r#"
-    SELECT c.user_id
-      FROM falukant_data.character c
-     WHERE c.region_id = $1
-       AND c.user_id IS NOT NULL;
-"#;
-
 impl StockageManager {
     pub fn new(pool: ConnectionPool, broker: MessageBroker) -> Self {
         Self {