feat: schelet gateway FastAPI (API v1 + worker + dashboard + SQLite WAL)

Structura repo conform plan.md sect. 4, booteaza cu /healthz verde:
- app/main.py: FastAPI (lifespan init_db), /healthz (worker viu + last login + queue), /metrics
- app/api/v1: POST /v1/prezentari (enqueue + dedup idempotency UNIQUE), GET prezentari/{id}, nomenclator, mapari
- app/rar_client.py: client RAR real (login/JWT, nomenclator, postPrezentare, getFinalizate) cu User-Agent obligatoriu (fix WAF 403)
- app/worker: proces separat, claim atomic BEGIN IMMEDIATE, heartbeat, login+send (send dezactivat by default)
- app/web: dashboard Jinja2+HTMX (coada, banner alerta blocate, worker viu/mort, stari empty)
- app/db.py + schema.sql: SQLite WAL, tabele accounts/api_keys/operations_mapping/nomenclator_rar/submissions/worker_heartbeat
- app/idempotency.py + payload.py: hash continut canonic + builder payload (status FINALIZATA, fara tipPrestatie)
- Dockerfile + docker-compose.yml (api+worker, volum SQLite persistent, restart:always)
- tools/import_dbf.py: stub T5

Verificat live: login prin rar_client OK (token 259), nomenclator 18 coduri, worker heartbeat -> /healthz worker_alive=True.
Ramas: T3 validare Pydantic, T4 snapshot payload, T2 reconciliere/retry worker, T5 import DBF, auth API-key, middleware redactare creds, criptare PII.

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

app/payload.py

@@ -0,0 +1,41 @@
+"""Constructor payload postPrezentare (schelet — T4 il completeaza).
+
+Reguli din contract (docs/api-rar-contract.md):
+  - status mereu "FINALIZATA".
+  - tipPrestatie NU se trimite (server-generated GENERIC).
+  - odometruFinal ca string.
+  - sistemReparat trimis mereu (default "null").
+  - prestatii: [{codPrestatie, idPrezentare: null}].
+  - b64Image / odometruInitial optionale (se omit daca lipsesc).
+T4 adauga snapshot-test fata de exemplul oficial din contract.
+"""
+
+from __future__ import annotations
+
+from typing import Any
+
+
+def build_rar_payload(prezentare: dict[str, Any]) -> dict[str, Any]:
+    """Mapeaza o prezentare interna -> payload exact pentru RAR postPrezentare."""
+    prestatii = prezentare.get("prestatii") or []
+    payload: dict[str, Any] = {
+        "vin": (prezentare.get("vin") or "").strip().upper(),
+        "nrInmatriculare": (prezentare.get("nr_inmatriculare") or "").strip().upper(),
+        "dataPrestatie": prezentare.get("data_prestatie"),
+        "odometruFinal": str(prezentare.get("odometru_final") or "").strip(),
+        "odometruInitial": prezentare.get("odometru_initial"),
+        "prestatii": [
+            {
+                "codPrestatie": (p.get("cod_prestatie") if isinstance(p, dict) else getattr(p, "cod_prestatie", None)),
+                "idPrezentare": None,
+            }
+            for p in prestatii
+        ],
+        "sistemReparat": prezentare.get("sistem_reparat") or "null",
+        "status": "FINALIZATA",
+    }
+    if prezentare.get("obs"):
+        payload["obs"] = prezentare["obs"]
+    if prezentare.get("b64_image"):
+        payload["b64Image"] = prezentare["b64_image"]
+    return payload