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/models.py

@@ -1,27 +1,39 @@
-from dataclasses import dataclass
+from dataclasses import dataclass, field
 from datetime import datetime
 from enum import Enum
 
 
-class ReportType(Enum):
-    CONTENT = "content"
-    CONTENT_STATS = "content_stats"
-    FULL_AUDIT = "full_audit"
+class Depth(Enum):
+    BASIC = "basic"
+    STANDARD = "standard"
+    FULL = "full"
 
     @property
     def label(self) -> str:
         return {
-            ReportType.CONTENT: "Content Analysis",
-            ReportType.CONTENT_STATS: "Content + Stats",
-            ReportType.FULL_AUDIT: "Full Audit",
+            Depth.BASIC: "Basic",
+            Depth.STANDARD: "Standard",
+            Depth.FULL: "Full",
         }[self]
 
+
+class FocusArea(Enum):
+    PSYCHOLOGY = "psychology"
+    BUSINESS = "business"
+    MARKETING = "marketing"
+    CONTENT = "content"
+    AUDIENCE = "audience"
+    SENTIMENT = "sentiment"
+
     @property
-    def description(self) -> str:
+    def label(self) -> str:
         return {
-            ReportType.CONTENT: "Topics, tone, themes, content strategy",
-            ReportType.CONTENT_STATS: "Above + posting frequency, engagement patterns",
-            ReportType.FULL_AUDIT: "All above + sentiment, audience insights, recommendations",
+            FocusArea.PSYCHOLOGY: "Psychology & Influence",
+            FocusArea.BUSINESS: "Business & Monetization",
+            FocusArea.MARKETING: "Marketing & Growth",
+            FocusArea.CONTENT: "Content Strategy",
+            FocusArea.AUDIENCE: "Audience & Engagement",
+            FocusArea.SENTIMENT: "Sentiment Analysis",
         }[self]
 
 
@@ -33,3 +45,11 @@ class ChannelMessage:
     views: int | None = None
     forwards: int | None = None
     replies: int | None = None
+
+
+@dataclass
+class AnalysisSession:
+    channel: str
+    depth: Depth | None = None
+    focus_areas: list[FocusArea] = field(default_factory=list)
+    model_id: str | None = None