refactor: add modal/validation utils and partial App encapsulation

Quick wins refactoring (Variant 1):
- Created src/utils/modal_handler.rs (120+ lines)
  - 4 functions for modal handling (close, confirm, yes/no)
  - ModalAction enum for type-safe processing
  - English and Russian keyboard layout support
  - 4 unit tests
- Created src/utils/validation.rs (180+ lines)
  - 7 validation functions (empty, length, IDs, etc)
  - Covers all common validation patterns
  - 7 unit tests
- Partial App encapsulation:
  - Made config field private (readonly via app.config())
  - Added 30+ getter/setter methods
  - Updated ui/messages.rs to use config()
- Updated documentation:
  - REFACTORING_OPPORTUNITIES.md: #1 Complete, #5 Partial
  - CONTEXT.md: Added quick wins section

Tests: 563 passed, 0 failed

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/app/mod.rs

@@ -44,18 +44,19 @@ use ratatui::widgets::ListState;
 /// app.select_current_chat();
 /// ```
 pub struct App {
-    pub config: crate::config::Config,
+    // Core (config - readonly через getter)
+    config: crate::config::Config,
     pub screen: AppScreen,
     pub td_client: TdClient,
     /// Состояние чата - type-safe state machine (новое!)
     pub chat_state: ChatState,
-    // Auth state
+    // Auth state (используются часто в UI)
     pub phone_input: String,
     pub code_input: String,
     pub password_input: String,
     pub error_message: Option<String>,
     pub status_message: Option<String>,
-    // Main app state
+    // Main app state (используются часто)
     pub chats: Vec<ChatInfo>,
     pub chat_list_state: ListState,
     pub selected_chat_id: Option<ChatId>,
@@ -800,4 +801,193 @@ impl App {
     pub fn get_selected_message_for_reaction(&self) -> Option<i64> {
         self.chat_state.selected_message_id().map(|id| id.as_i64())
     }
+
+    // ========== Getter/Setter методы для инкапсуляции ==========
+
+    // Config
+    pub fn config(&self) -> &crate::config::Config {
+        &self.config
+    }
+
+    // Screen
+    pub fn screen(&self) -> &AppScreen {
+        &self.screen
+    }
+
+    pub fn set_screen(&mut self, screen: AppScreen) {
+        self.screen = screen;
+    }
+
+    // Auth state
+    pub fn phone_input(&self) -> &str {
+        &self.phone_input
+    }
+
+    pub fn phone_input_mut(&mut self) -> &mut String {
+        &mut self.phone_input
+    }
+
+    pub fn set_phone_input(&mut self, input: String) {
+        self.phone_input = input;
+    }
+
+    pub fn code_input(&self) -> &str {
+        &self.code_input
+    }
+
+    pub fn code_input_mut(&mut self) -> &mut String {
+        &mut self.code_input
+    }
+
+    pub fn set_code_input(&mut self, input: String) {
+        self.code_input = input;
+    }
+
+    pub fn password_input(&self) -> &str {
+        &self.password_input
+    }
+
+    pub fn password_input_mut(&mut self) -> &mut String {
+        &mut self.password_input
+    }
+
+    pub fn set_password_input(&mut self, input: String) {
+        self.password_input = input;
+    }
+
+    pub fn error_message(&self) -> Option<&str> {
+        self.error_message.as_deref()
+    }
+
+    pub fn set_error_message(&mut self, message: Option<String>) {
+        self.error_message = message;
+    }
+
+    pub fn status_message(&self) -> Option<&str> {
+        self.status_message.as_deref()
+    }
+
+    pub fn set_status_message(&mut self, message: Option<String>) {
+        self.status_message = message;
+    }
+
+    // Main app state
+    pub fn chats(&self) -> &[ChatInfo] {
+        &self.chats
+    }
+
+    pub fn chats_mut(&mut self) -> &mut Vec<ChatInfo> {
+        &mut self.chats
+    }
+
+    pub fn set_chats(&mut self, chats: Vec<ChatInfo>) {
+        self.chats = chats;
+    }
+
+    pub fn chat_list_state(&self) -> &ListState {
+        &self.chat_list_state
+    }
+
+    pub fn chat_list_state_mut(&mut self) -> &mut ListState {
+        &mut self.chat_list_state
+    }
+
+    pub fn selected_chat_id(&self) -> Option<ChatId> {
+        self.selected_chat_id
+    }
+
+    pub fn set_selected_chat_id(&mut self, id: Option<ChatId>) {
+        self.selected_chat_id = id;
+    }
+
+    pub fn message_input(&self) -> &str {
+        &self.message_input
+    }
+
+    pub fn message_input_mut(&mut self) -> &mut String {
+        &mut self.message_input
+    }
+
+    pub fn set_message_input(&mut self, input: String) {
+        self.message_input = input;
+    }
+
+    pub fn cursor_position(&self) -> usize {
+        self.cursor_position
+    }
+
+    pub fn set_cursor_position(&mut self, pos: usize) {
+        self.cursor_position = pos;
+    }
+
+    pub fn message_scroll_offset(&self) -> usize {
+        self.message_scroll_offset
+    }
+
+    pub fn set_message_scroll_offset(&mut self, offset: usize) {
+        self.message_scroll_offset = offset;
+    }
+
+    pub fn selected_folder_id(&self) -> Option<i32> {
+        self.selected_folder_id
+    }
+
+    pub fn set_selected_folder_id(&mut self, id: Option<i32>) {
+        self.selected_folder_id = id;
+    }
+
+    pub fn is_loading(&self) -> bool {
+        self.is_loading
+    }
+
+    pub fn set_loading(&mut self, loading: bool) {
+        self.is_loading = loading;
+    }
+
+    // Search state
+    pub fn is_searching(&self) -> bool {
+        self.is_searching
+    }
+
+    pub fn set_searching(&mut self, searching: bool) {
+        self.is_searching = searching;
+    }
+
+    pub fn search_query(&self) -> &str {
+        &self.search_query
+    }
+
+    pub fn search_query_mut(&mut self) -> &mut String {
+        &mut self.search_query
+    }
+
+    pub fn set_search_query(&mut self, query: String) {
+        self.search_query = query;
+    }
+
+    // Redraw flag
+    pub fn needs_redraw(&self) -> bool {
+        self.needs_redraw
+    }
+
+    pub fn set_needs_redraw(&mut self, redraw: bool) {
+        self.needs_redraw = redraw;
+    }
+
+    pub fn mark_for_redraw(&mut self) {
+        self.needs_redraw = true;
+    }
+
+    // Typing indicator
+    pub fn last_typing_sent(&self) -> Option<std::time::Instant> {
+        self.last_typing_sent
+    }
+
+    pub fn set_last_typing_sent(&mut self, time: Option<std::time::Instant>) {
+        self.last_typing_sent = time;
+    }
+
+    pub fn update_last_typing_sent(&mut self) {
+        self.last_typing_sent = Some(std::time::Instant::now());
+    }
 }