feat(fsn-db): add apply_schema() to DbConnection for idempotent raw SQL schema init

Author: FreeSynergy

fsn-db/src/connection.rs

@@ -1,6 +1,6 @@
 // Database connection management via SeaORM.
 
-use sea_orm::{ConnectOptions, Database, DatabaseConnection};
+use sea_orm::{ConnectOptions, ConnectionTrait, Database, DatabaseConnection, Statement};
 
 use fsn_error::FsnError;
 
@@ -69,6 +69,22 @@ impl DbConnection {
         &self.backend
     }
 
+    /// Execute all statements in a schema string, creating tables if they don't exist.
+    ///
+    /// Safe to call every startup — designed for idempotent `CREATE TABLE IF NOT EXISTS` schemas.
+    pub async fn apply_schema(&self, schema: &str) -> Result<(), FsnError> {
+        for stmt in schema.split(';').map(str::trim).filter(|s| !s.is_empty()) {
+            self.conn
+                .execute(Statement::from_string(
+                    self.conn.get_database_backend(),
+                    stmt.to_string(),
+                ))
+                .await
+                .map_err(|e| FsnError::internal(format!("schema apply: {e}")))?;
+        }
+        Ok(())
+    }
+
     /// Close the connection pool.
     pub async fn close(self) -> Result<(), FsnError> {
         self.conn