refactor: complete Phase 13 deep architecture refactoring (etaps 3-7)

Split monolithic files into modular architecture:
- ui/messages.rs (893→365 lines): extract modals/, compose_bar.rs
- tdlib/messages.rs (836→3 files): split into messages/mod, convert, operations
- config/mod.rs (642→3 files): extract validation.rs, loader.rs
- Code duplication cleanup: shared components, ~220 lines removed
- Documentation: PROJECT_STRUCTURE.md rewrite, 16 files got //! docs

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/tdlib/messages/convert.rs

@@ -0,0 +1,136 @@
+//! TDLib message conversion: JSON → MessageInfo, reply info fetching.
+
+use crate::types::{ChatId, MessageId};
+use tdlib_rs::functions;
+use tdlib_rs::types::Message as TdMessage;
+
+use crate::tdlib::types::{MessageBuilder, MessageInfo};
+
+use super::MessageManager;
+
+impl MessageManager {
+    /// Конвертировать TdMessage в MessageInfo
+    pub(crate) async fn convert_message(&self, msg: &TdMessage) -> Option<MessageInfo> {
+        use crate::tdlib::message_conversion::{
+            extract_content_text, extract_entities, extract_forward_info,
+            extract_reactions, extract_reply_info, extract_sender_name,
+        };
+
+        // Извлекаем все части сообщения используя вспомогательные функции
+        let content_text = extract_content_text(msg);
+        let entities = extract_entities(msg);
+        let sender_name = extract_sender_name(msg, self.client_id).await;
+        let forward_from = extract_forward_info(msg);
+        let reply_to = extract_reply_info(msg);
+        let reactions = extract_reactions(msg);
+
+        let mut builder = MessageBuilder::new(MessageId::new(msg.id))
+            .sender_name(sender_name)
+            .text(content_text)
+            .entities(entities)
+            .date(msg.date)
+            .edit_date(msg.edit_date);
+
+        if msg.is_outgoing {
+            builder = builder.outgoing();
+        } else {
+            builder = builder.incoming();
+        }
+
+        if !msg.contains_unread_mention {
+            builder = builder.read();
+        } else {
+            builder = builder.unread();
+        }
+
+        if msg.can_be_edited {
+            builder = builder.editable();
+        }
+
+        if msg.can_be_deleted_only_for_self {
+            builder = builder.deletable_for_self();
+        }
+
+        if msg.can_be_deleted_for_all_users {
+            builder = builder.deletable_for_all();
+        }
+
+        if let Some(reply) = reply_to {
+            builder = builder.reply_to(reply);
+        }
+
+        if let Some(forward) = forward_from {
+            builder = builder.forward_from(forward);
+        }
+
+        builder = builder.reactions(reactions);
+
+        Some(builder.build())
+    }
+
+    /// Загружает недостающую информацию об исходных сообщениях для ответов.
+    ///
+    /// Ищет все reply-сообщения с `sender_name == "Unknown"` и загружает
+    /// полную информацию (имя отправителя, текст) из TDLib.
+    ///
+    /// # Note
+    ///
+    /// Вызывайте после загрузки истории чата для заполнения информации о цитируемых сообщениях.
+    pub async fn fetch_missing_reply_info(&mut self) {
+        // Early return if no chat selected
+        let Some(chat_id) = self.current_chat_id else {
+            return;
+        };
+
+        // Collect message IDs with missing reply info using filter_map
+        let to_fetch: Vec<MessageId> = self
+            .current_chat_messages
+            .iter()
+            .filter_map(|msg| {
+                msg.interactions
+                    .reply_to
+                    .as_ref()
+                    .filter(|reply| reply.sender_name == "Unknown")
+                    .map(|reply| reply.message_id)
+            })
+            .collect();
+
+        // Fetch and update each missing message
+        for message_id in to_fetch {
+            self.fetch_and_update_reply(chat_id, message_id).await;
+        }
+    }
+
+    /// Загружает одно сообщение и обновляет reply информацию.
+    async fn fetch_and_update_reply(&mut self, chat_id: ChatId, message_id: MessageId) {
+        // Try to fetch the original message
+        let Ok(original_msg_enum) =
+            functions::get_message(chat_id.as_i64(), message_id.as_i64(), self.client_id).await
+        else {
+            return;
+        };
+
+        let tdlib_rs::enums::Message::Message(original_msg) = original_msg_enum;
+        let Some(orig_info) = self.convert_message(&original_msg).await else {
+            return;
+        };
+
+        // Extract text preview (first 50 chars)
+        let text_preview: String = orig_info
+            .content
+            .text
+            .chars()
+            .take(50)
+            .collect();
+
+        // Update reply info in all messages that reference this message
+        self.current_chat_messages
+            .iter_mut()
+            .filter_map(|msg| msg.interactions.reply_to.as_mut())
+            .filter(|reply| reply.message_id == message_id)
+            .for_each(|reply| {
+                reply.sender_name = orig_info.metadata.sender_name.clone();
+                reply.text = text_preview.clone();
+            });
+    }
+}