feat(llm): full multi-tier S/A/B/C/D with routing + pricing

Estende ModelTier a 5 livelli (S/A/B/C/D) con routing automatico:
S/A/B via Anthropic SDK, C/D via OpenRouter (OpenAI SDK). Aggiunge
prezzi per tier S (Opus), A (Sonnet placeholder) e D (Llama). Refactor
LLMClient.complete con dispatch tramite tier_models map e helper
_call_anthropic / _call_openrouter. Settings esposte per tutti e 5
i modelli env-configurabili.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/run_phase1.py

@@ -48,8 +48,11 @@ def main() -> None:
             settings.anthropic_api_key.get_secret_value()
             if settings.anthropic_api_key else None
         ),
-        model_tier_c=settings.llm_model_tier_c,
+        model_tier_s=settings.llm_model_tier_s,
+        model_tier_a=settings.llm_model_tier_a,
         model_tier_b=settings.llm_model_tier_b,
+        model_tier_c=settings.llm_model_tier_c,
+        model_tier_d=settings.llm_model_tier_d,
         openrouter_base_url=settings.openrouter_base_url,
     )