Fechamento de Caixa - Tauri 2 initial commit

- Storage: SQLite local via rusqlite
- Supabase: REST API via reqwest
- Printer: USB ESC/POS for TM-T20
- Frontend: vanilla HTML (form-v9.3 ported)
- Build: GitHub Actions for Linux/Windows/macOS

src-tauri/src/plugins/app.rs

@@ -0,0 +1,87 @@
+//! Plugin de configuração da aplicação (loja, preferências)
+//! Persistido em config.json ao lado do banco SQLite.
+
+use serde::{Deserialize, Serialize};
+use std::fs;
+use std::path::PathBuf;
+use std::sync::Mutex;
+use tauri::State;
+
+#[derive(Debug, Serialize, Deserialize, Clone)]
+pub struct AppConfig {
+    pub loja: String,
+    pub pdv_nome: String,
+    pub operador_default: String,
+    pub turno_default: String,
+    pub sync_automatico: bool,
+    pub auto_open_printer: bool,
+}
+
+impl Default for AppConfig {
+    fn default() -> Self {
+        Self {
+            loja: "Uniao".to_string(),
+            pdv_nome: "PDV-01".to_string(),
+            operador_default: String::new(),
+            turno_default: String::new(),
+            sync_automatico: true,
+            auto_open_printer: false,
+        }
+    }
+}
+
+pub struct AppState {
+    pub config: Mutex<AppConfig>,
+    config_path: PathBuf,
+}
+
+impl AppState {
+    pub fn new(data_dir: PathBuf) -> Self {
+        let config_path = data_dir.join("config.json");
+        let config = if let Ok(content) = fs::read_to_string(&config_path) {
+            serde_json::from_str(&content).unwrap_or_default()
+        } else {
+            AppConfig::default()
+        };
+
+        Self {
+            config: Mutex::new(config),
+            config_path,
+        }
+    }
+
+    pub fn save(&self) -> Result<(), String> {
+        let cfg = self.config.lock().map_err(|_| "lock error")?;
+        let json = serde_json::to_string_pretty(&*cfg)
+            .map_err(|e| e.to_string())?;
+        fs::write(&self.config_path, json).map_err(|e| e.to_string())?;
+        log::info!("Config salvo em {:?}", self.config_path);
+        Ok(())
+    }
+}
+
+#[tauri::command]
+pub fn get_loja(state: State<'_, AppState>) -> String {
+    state.config.lock().unwrap().loja.clone()
+}
+
+#[tauri::command]
+pub fn set_loja(state: State<'_, AppState>, loja: String) -> Result<(), String> {
+    state.config.lock().unwrap().loja = loja;
+    state.save()
+}
+
+#[tauri::command]
+pub fn get_config(state: State<'_, AppState>) -> AppConfig {
+    state.config.lock().unwrap().clone()
+}
+
+#[tauri::command]
+pub fn set_config(state: State<'_, AppState>, cfg: AppConfig) -> Result<(), String> {
+    *state.config.lock().unwrap() = cfg;
+    state.save()
+}
+
+pub fn init(data_dir: PathBuf) -> AppState {
+    AppState::new(data_dir)
+}