T1: restructure to domain/application/infrastructure + schema version 1

- Move cashflow_model/ -> domain/
- Move engine/ -> application/
- Move cli/, sync/, ai/ -> infrastructure/
- Update all imports across codebase and tests
- Add version=1 to FinancialModel.to_dict() with migration hook in from_dict
- Update pyproject.toml: cf entry point and packages.find

Tests: 63/63 pass.

infrastructure/ai/prompts.py

@@ -0,0 +1,21 @@
+from infrastructure.cli.i18n import t
+
+ANALYZE_PROMPT = t("prompt.analyze")
+ADVICE_PROMPT = t("prompt.advice")
+SCENARIO_COMPARISON_PROMPT = t("prompt.scenario_comparison")
+
+
+def format_context(
+    model_json: str,
+    forecast_json: str,
+    months: int = 12,
+    base_currency: str = "RUB",
+    display_currency: str = "RUB",
+) -> str:
+    return ANALYZE_PROMPT.format(
+        model_json=model_json,
+        forecast_json=forecast_json,
+        months=months,
+        base_currency=base_currency,
+        display_currency=display_currency,
+    )