T5: Dependency Injection — services через composition root

- AssistantService теперь принимает ForecastService в конструкторе
  (раньше создавал new ForecastService() внутри analyze/advice)
- infrastructure/cli/main.py: _build_services() — composition root,
  собирает граф ForecastService, ScenarioService, AssistantService, CurrencyConverter
- Все CLI-команды используют _build_services(model) вместо прямого new
- test_ai.py: обновлён под новый контракт AssistantService

Tests: 67/67 pass.

tests/test_ai.py

@@ -1,24 +1,19 @@
+from application.forecast import ForecastService
 from infrastructure.ai.assistant import AssistantService
-from infrastructure.ai.prompts import ADVICE_PROMPT, ANALYZE_PROMPT
 
 
 class TestAssistantService:
     def test_analyze_returns_prompt(self, sample_model):
-        assistant = AssistantService(sample_model)
+        forecast_service = ForecastService(sample_model)
+        assistant = AssistantService(sample_model, forecast_service=forecast_service)
         result = assistant.analyze(months=6)
         assert "prompt" in result
         assert "summary" in result
-        assert "forecast" in result
         assert result["ai_response"] is None
 
     def test_advice_returns_prompt(self, sample_model):
-        assistant = AssistantService(sample_model)
+        forecast_service = ForecastService(sample_model)
+        assistant = AssistantService(sample_model, forecast_service=forecast_service)
         result = assistant.advice("Как мне сэкономить?", months=6)
         assert "prompt" in result
         assert "ai_response" in result
-
-    def test_prompt_templates(self):
-        assert "{model_json}" in ANALYZE_PROMPT
-        assert "{forecast_json}" in ANALYZE_PROMPT
-        assert "{model_json}" in ADVICE_PROMPT
-        assert "{question}" in ADVICE_PROMPT