feat: implement main application structure with UI and layout management

- Added main application logic in `src/ui/app.rs` to handle state and modal dialogs.
- Created module structure for UI components in `src/ui/mod.rs`.
- Implemented column configuration screen in `src/ui/screens/configuracao_colunas.rs`.
- Developed file import screen in `src/ui/screens/import.rs` for CSV and XLSX files.
- Added layout management screen in `src/ui/screens/layouts.rs` for saving and importing layouts.
- Created result display screen in `src/ui/screens/resultado.rs` to show analysis results.
- Introduced modular organization for screens in `src/ui/screens/mod.rs`.

src/domain/entities/serie.rs

@@ -0,0 +1,58 @@
+use crate::domain::errors::ErroSerie;
+use regex::Regex;
+use std::sync::OnceLock;
+
+static REGEX_SERIE: OnceLock<Regex> = OnceLock::new();
+
+fn regex_serie() -> &'static Regex {
+    REGEX_SERIE.get_or_init(|| Regex::new(r"^[0-9]{1,3}$").expect("Regex de série inválida"))
+}
+
+/// Valida e normaliza uma série.
+/// Retorna `Ok(serie_normalizada)` ou `Err(ErroSerie)`.
+pub fn validar_serie(s: &str) -> Result<String, ErroSerie> {
+    let trimmed = s.trim();
+    if trimmed.is_empty() {
+        return Err(ErroSerie::Vazia);
+    }
+    if regex_serie().is_match(trimmed) {
+        Ok(trimmed.to_string())
+    } else {
+        Err(ErroSerie::Invalida(trimmed.to_string()))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn serie_valida_simples() {
+        assert!(validar_serie("1").is_ok());
+        assert!(validar_serie("01").is_ok());
+        assert!(validar_serie("001").is_ok());
+        assert!(validar_serie("999").is_ok());
+    }
+
+    #[test]
+    fn serie_com_espacos_e_valida() {
+        assert!(validar_serie("  1  ").is_ok());
+    }
+
+    #[test]
+    fn serie_invalida_letras() {
+        assert!(validar_serie("ABC").is_err());
+        assert!(validar_serie("1A").is_err());
+    }
+
+    #[test]
+    fn serie_invalida_quatro_digitos() {
+        assert!(validar_serie("1234").is_err());
+    }
+
+    #[test]
+    fn serie_vazia() {
+        assert!(matches!(validar_serie(""), Err(ErroSerie::Vazia)));
+        assert!(matches!(validar_serie("   "), Err(ErroSerie::Vazia)));
+    }
+}