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

bot/services/ai_client.py

@@ -0,0 +1,106 @@
+import json
+import logging
+from abc import ABC, abstractmethod
+from collections.abc import Callable, Coroutine
+from typing import Any
+
+import anthropic
+import httpx
+
+from bot.config import settings
+
+log = logging.getLogger(__name__)
+
+ProgressCallback = Callable[[str], Coroutine[Any, Any, None]]
+
+
+class AIClient(ABC):
+    @abstractmethod
+    async def complete(
+        self,
+        system: str,
+        user: str,
+        max_tokens: int,
+        on_progress: ProgressCallback | None = None,
+    ) -> str: ...
+
+
+class AnthropicClient(AIClient):
+    def __init__(self, model_id: str) -> None:
+        self.model_id = model_id
+        self.client = anthropic.AsyncAnthropic(api_key=settings.anthropic_api_key)
+
+    async def complete(
+        self,
+        system: str,
+        user: str,
+        max_tokens: int,
+        on_progress: ProgressCallback | None = None,
+    ) -> str:
+        kwargs: dict[str, Any] = {
+            "model": self.model_id,
+            "max_tokens": max_tokens,
+            "system": system,
+            "messages": [{"role": "user", "content": user}],
+        }
+        if "opus-4-6" in self.model_id:
+            kwargs["thinking"] = {"type": "adaptive"}
+
+        async with self.client.messages.stream(**kwargs) as stream:
+            response = await stream.get_final_message()
+
+        return "".join(
+            block.text for block in response.content if block.type == "text"
+        )
+
+
+class OpenRouterClient(AIClient):
+    BASE_URL = "https://openrouter.ai/api/v1/chat/completions"
+
+    def __init__(self, model_id: str) -> None:
+        self.model_id = model_id
+
+    async def complete(
+        self,
+        system: str,
+        user: str,
+        max_tokens: int,
+        on_progress: ProgressCallback | None = None,
+    ) -> str:
+        headers = {
+            "Authorization": f"Bearer {settings.openrouter_api_key}",
+            "Content-Type": "application/json",
+        }
+        payload = {
+            "model": self.model_id,
+            "max_tokens": max_tokens,
+            "messages": [
+                {"role": "system", "content": system},
+                {"role": "user", "content": user},
+            ],
+            "stream": True,
+        }
+
+        collected = []
+        async with httpx.AsyncClient(timeout=300) as client:
+            async with client.stream("POST", self.BASE_URL, headers=headers, json=payload) as resp:
+                resp.raise_for_status()
+                async for line in resp.aiter_lines():
+                    if not line.startswith("data: "):
+                        continue
+                    data = line[6:]
+                    if data == "[DONE]":
+                        break
+                    chunk = json.loads(data)
+                    delta = chunk.get("choices", [{}])[0].get("delta", {})
+                    content = delta.get("content", "")
+                    if content:
+                        collected.append(content)
+
+        return "".join(collected)
+
+
+def get_ai_client(model_id: str) -> AIClient:
+    if "/" in model_id:
+        return OpenRouterClient(model_id)
+    return AnthropicClient(model_id)