refactor: eliminate code duplication - extract helpers and use retry utils

Extracted duplicate code and unified timeout handling across the codebase.

Changes:
- Extracted open_chat_and_load_data() function (eliminates 52 lines of duplication)
- Replaced manual y/н/Enter handling with handle_yes_no() from modal_handler (2 places)
- Replaced 7 direct tokio::time::timeout calls with retry utils (auth, main_input, main)
- Added with_timeout_ignore() for non-critical operations
- Fixed modal_handler.rs bug: corrected Russian 'y' key (д → н)
- Removed unused imports in handlers/mod.rs and utils/mod.rs

Impact:
- main_input.rs: 1164 → 958 lines (-206 lines, -18%)
- Code duplication: 52 lines eliminated
- Direct timeout calls: 7 → 1 (-86%)
- DRY principle applied throughout

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

src/utils/modal_handler.rs

@@ -106,7 +106,7 @@ pub fn should_confirm_modal(key_code: KeyCode) -> bool {
 ///
 /// assert_eq!(handle_yes_no(KeyCode::Char('y')), Some(true));
 /// assert_eq!(handle_yes_no(KeyCode::Char('Y')), Some(true));
-/// assert_eq!(handle_yes_no(KeyCode::Char('д')), Some(true)); // русская 'y'
+/// assert_eq!(handle_yes_no(KeyCode::Char('н')), Some(true)); // русская 'y'
 /// assert_eq!(handle_yes_no(KeyCode::Enter), Some(true));
 ///
 /// assert_eq!(handle_yes_no(KeyCode::Char('n')), Some(false));
@@ -118,7 +118,7 @@ pub fn should_confirm_modal(key_code: KeyCode) -> bool {
 pub fn handle_yes_no(key_code: KeyCode) -> Option<bool> {
     match key_code {
         // Yes - подтверждение (английская и русская раскладка)
-        KeyCode::Char('y') | KeyCode::Char('Y') | KeyCode::Char('д') | KeyCode::Char('Д') => {
+        KeyCode::Char('y') | KeyCode::Char('Y') | KeyCode::Char('н') | KeyCode::Char('Н') => {
             Some(true)
         }
         KeyCode::Enter => Some(true),
@@ -165,8 +165,8 @@ mod tests {
         // Yes variants
         assert_eq!(handle_yes_no(KeyCode::Char('y')), Some(true));
         assert_eq!(handle_yes_no(KeyCode::Char('Y')), Some(true));
-        assert_eq!(handle_yes_no(KeyCode::Char('д')), Some(true)); // Russian
-        assert_eq!(handle_yes_no(KeyCode::Char('Д')), Some(true)); // Russian
+        assert_eq!(handle_yes_no(KeyCode::Char('н')), Some(true)); // Russian
+        assert_eq!(handle_yes_no(KeyCode::Char('Н')), Some(true)); // Russian
         assert_eq!(handle_yes_no(KeyCode::Enter), Some(true));
 
         // No variants