feat(5.20): US-004/005/006/009 ingestie+API+worker+import pe mediu RAR

US-004: rezolva_rar_env (cerere>default cont>ancora globala) + MediuIndisponibil
+ cod RAR_MEDIU_INDISPONIBIL.
US-005: camp rar_env pe POST /v1/prezentari + /valideaza (Literal), echo in
SubmissionResult/ValidareResult/GET, build_key + INSERT env-aware.
US-006: AccountSessions re-cheiat (account_id, rar_env); RarClient base_url per
env; creds din slotul env; purge + recover_orphans scoped pe env (E1/1a, 1b/E6);
claim_one propaga rar_env (1c/E8); keepalive pe ancora globala (M2).
US-009: selector mediu la import (>=2 medii), eticheta la 1, banner la 0; commit
seteaza rar_env pe submissions.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/rar_client.py

@@ -44,6 +44,11 @@ class RarAuthError(RarError):
     """Login esuat (401 / credentiale invalide). NU se face retry."""
 
 
+def base_url_pentru_env(settings: "Settings", env: str) -> str:
+    """URL de baza al mediului RAR: 'prod' -> rar_base_url_prod, altfel rar_base_url_test."""
+    return settings.rar_base_url_prod if env == "prod" else settings.rar_base_url_test
+
+
 class RarClient:
     """Client sincron httpx. Folosit din worker (proces separat).
 
@@ -53,10 +58,10 @@ class RarClient:
             data = rar.post_prezentare(token, payload)
     """
 
-    def __init__(self, settings: Settings | None = None):
+    def __init__(self, settings: Settings | None = None, *, base_url: str | None = None):
         self.settings = settings or get_settings()
         self._client = httpx.Client(
-            base_url=self.settings.rar_base_url,
+            base_url=base_url if base_url is not None else self.settings.rar_base_url,
             timeout=self.settings.http_timeout_s,
             headers={"User-Agent": self.settings.http_user_agent},  # fix WAF 403
         )