Fix HOME volume mount, genericize topic, add progress statuses, extract lexicon

- Volume was mounted at ~/.claude only, but claude-code writes auth to
  ~/.claude.json too — that file lived on the ephemeral container layer and
  was lost on every recreate. Now the whole $HOME is on the named volume,
  and claude-config moved outside HOME (/app) so it isn't shadowed by it.
- Default /news topic was hardcoded to AI; now it's a configurable
  DEFAULT_TOPIC (plain "главные новости дня"), topic is fully free-form.
- Prompt now instructs Claude to send interim "⏳ ..." progress updates via
  send_to_telegram while researching, not just the final digest — a bare
  request like "call this tool" was already taking 3+ minutes end-to-end,
  so silence read as broken.
- All user-facing/prompt text moved into bot/lib/lexicon.dart.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

bot/lib/config.dart

@@ -1,16 +1,17 @@
 import 'dart:io';
+import 'lexicon.dart';
 
 class Config {
   final String telegramToken;
   final Set<int> allowedChatIds;
-  final String newsPrompt;
+  final String defaultTopic;
   final int claudeTimeoutSeconds;
   final String mcpConfigPath;
 
   Config({
     required this.telegramToken,
     required this.allowedChatIds,
-    required this.newsPrompt,
+    required this.defaultTopic,
     required this.claudeTimeoutSeconds,
     required this.mcpConfigPath,
   });
@@ -27,14 +28,10 @@ class Config {
     return Config(
       telegramToken: e['TELEGRAM_BOT_TOKEN'] ?? '',
       allowedChatIds: allowed,
-      newsPrompt: e['NEWS_PROMPT'] ??
-          'Проведи ресёрч последних новостей и трендов в области искусственного '
-              'интеллекта за последние 7 дней. Используй поиск в интернете. '
-              'Составь краткую выжимку: 5-8 пунктов, у каждого — суть в 1-2 '
-              'предложениях и ссылка на источник.',
+      defaultTopic: e['DEFAULT_TOPIC'] ?? Lexicon.defaultTopic,
       claudeTimeoutSeconds:
-          int.tryParse(e['CLAUDE_TIMEOUT_SECONDS'] ?? '360') ?? 360,
-      mcpConfigPath: e['MCP_CONFIG_PATH'] ?? '/home/agent/claude-config/mcp.json',
+          int.tryParse(e['CLAUDE_TIMEOUT_SECONDS'] ?? '600') ?? 600,
+      mcpConfigPath: e['MCP_CONFIG_PATH'] ?? '/app/claude-config/mcp.json',
     );
   }
 }