Add multi-user features: i18n, payments, multi-model AI, focus areas

Replace single report type with composable analysis: depth levels
(basic/standard/full) + focus area multi-select (psychology, business,
marketing, content, audience, sentiment). Multi-step inline keyboard
flow guides users through selection.

- i18n: English + Russian, auto-detect from Telegram, /lang override
- AI providers: Anthropic + OpenRouter via AIClient abstraction
- Telegram Stars payments with per-depth pricing and free trial
- SQLite (aiosqlite) for users, analyses, payments tracking
- User middleware for auto-registration and language detection
- Report persistence: save .md locally, offer file download
- New commands: /features, /prices, /lang
- Composable prompt system: depth modifiers + focus area fragments

pyproject.toml

@@ -1,10 +1,11 @@
 [project]
 name = "tg-channel-analyzer"
-version = "0.1.0"
+version = "0.2.0"
 requires-python = ">=3.11"
 dependencies = [
     "aiogram>=3.24,<4",
     "telethon>=1.42,<2",
     "anthropic>=0.80,<1",
     "pydantic-settings>=2.0",
+    "aiosqlite>=0.20",
 ]