Refactor schedule and user repositories into modular structure

- Moved schedule repository logic into separate modules for SQLite and PostgreSQL implementations.
- Created a mapping module for shared data structures and mapping functions in the schedule repository.
- Added new mapping module for user repository to handle user data transformations.
- Implemented PostgreSQL and SQLite user repository adapters with necessary CRUD operations.
- Added tests for user repository functionality, including saving, finding, and deleting users.

k-tv-backend/infra/src/user_repository/mapping.rs

@@ -0,0 +1,42 @@
+use chrono::{DateTime, Utc};
+use sqlx::FromRow;
+use uuid::Uuid;
+
+use domain::{DomainError, Email, User};
+
+#[derive(Debug, FromRow)]
+pub(super) struct UserRow {
+    pub id: String,
+    pub subject: String,
+    pub email: String,
+    pub password_hash: Option<String>,
+    pub created_at: String,
+}
+
+impl TryFrom<UserRow> for User {
+    type Error = DomainError;
+
+    fn try_from(row: UserRow) -> Result<Self, Self::Error> {
+        let id = Uuid::parse_str(&row.id)
+            .map_err(|e| DomainError::RepositoryError(format!("Invalid UUID: {}", e)))?;
+        let created_at = DateTime::parse_from_rfc3339(&row.created_at)
+            .map(|dt| dt.with_timezone(&Utc))
+            .or_else(|_| {
+                // Fallback for SQLite datetime format
+                chrono::NaiveDateTime::parse_from_str(&row.created_at, "%Y-%m-%d %H:%M:%S")
+                    .map(|dt| dt.and_utc())
+            })
+            .map_err(|e| DomainError::RepositoryError(format!("Invalid datetime: {}", e)))?;
+
+        let email = Email::try_from(row.email)
+            .map_err(|e| DomainError::RepositoryError(format!("Invalid email in DB: {}", e)))?;
+
+        Ok(User::with_id(
+            id,
+            row.subject,
+            email,
+            row.password_hash,
+            created_at,
+        ))
+    }
+}