chore: clean Rust warnings and remove unused deps

- Remove serde_yaml and tokio from Cargo.toml (unused)
- Add #[allow(dead_code)] to utility code kept for future use
  (CUT_FULL, ALIGN_RIGHT, line(), PrinterError, SupabaseError,
   atualizar_sync, remover, Lock variant)
- Zero compiler warnings on release build

src-tauri/src/plugins/escpos.rs

@@ -8,6 +8,7 @@ pub const LF: &[u8] = b"\x0A";
 /// Cortar papel (parcial)
 pub const CUT: &[u8] = b"\x1D\x56\x01";
 /// Cortar papel (total)
+#[allow(dead_code)]
 pub const CUT_FULL: &[u8] = b"\x1D\x56\x00";
 /// Alimentar 3 linhas antes de cortar
 pub const FEED_CUT: &[u8] = b"\x1B\x64\x03";
@@ -17,6 +18,7 @@ pub const BOLD_OFF: &[u8] = b"\x1B\x45\x00";
 /// Alinhamento
 pub const ALIGN_LEFT: &[u8] = b"\x1B\x61\x00";
 pub const ALIGN_CENTER: &[u8] = b"\x1B\x61\x01";
+#[allow(dead_code)]
 pub const ALIGN_RIGHT: &[u8] = b"\x1B\x61\x02";
 /// Fonte normal / dupla
 pub const FONT_NORMAL: &[u8] = b"\x1B\x21\x00";
@@ -38,6 +40,7 @@ pub fn title(text: &str) -> Vec<u8> {
 }
 
 /// Monta linha normal (alinhada à esquerda)
+#[allow(dead_code)]
 pub fn line(text: &str) -> Vec<u8> {
     let mut out = Vec::new();
     out.extend_from_slice(ALIGN_LEFT);

src-tauri/src/plugins/printer.rs

@@ -5,6 +5,7 @@ use std::sync::Mutex;
 use thiserror::Error;
 
 #[derive(Error, Debug)]
+#[allow(dead_code)]
 pub enum PrinterError {
     #[error("Impressora não encontrada. Verifique se está conectada via USB e ligada.")]
     NotFound,

src-tauri/src/plugins/storage.rs

@@ -335,6 +335,7 @@ impl DbManager {
     }
 
     /// Atualiza sync_status de um registro.
+    #[allow(dead_code)]
     pub fn atualizar_sync(&self, uuid: &str, status: SyncStatus) -> Result<(), StorageError> {
         let conn = self.conn.lock().map_err(|_| StorageError::Lock)?;
         let now = Utc::now().format("%Y-%m-%dT%H:%M:%S%.3fZ").to_string();
@@ -346,6 +347,7 @@ impl DbManager {
     }
 
     /// Remove um registro (para debugging).
+    #[allow(dead_code)]
     pub fn remover(&self, uuid: &str) -> Result<bool, StorageError> {
         let conn = self.conn.lock().map_err(|_| StorageError::Lock)?;
         let n = conn.execute("DELETE FROM fechamentos WHERE uuid = ?1", params![uuid])?;
@@ -508,7 +510,7 @@ pub fn carregar_rascunho(
             // Simplifica para formato que o frontend espera
             let total_sangrias: f64 = e.tabelas.sangrias.iter().filter_map(|r| r.valor).sum();
             let total_despesas: f64 = e.tabelas.despesas.iter().filter_map(|r| r.valor).sum();
-            let total_receber: f64 = e.tabelas.areceber.iter().filter_map(|r| r.valor).sum();
+            let _total_receber: f64 = e.tabelas.areceber.iter().filter_map(|r| r.valor).sum();
             let despesa_rows: Vec<_> = e.tabelas.despesas.iter().filter_map(|r| {
                 r.descricao.as_ref().map(|d| serde_json::json!({"desc": d, "valor": r.valor}))
             }).collect();

src-tauri/src/plugins/supabase.rs

@@ -8,6 +8,7 @@ use tauri::State;
 use thiserror::Error;
 
 #[derive(Error, Debug)]
+#[allow(dead_code)]
 pub enum SupabaseError {
     #[error("HTTP error: {0}")]
     Http(#[from] reqwest::Error),