feat(T2): reconciliere anti-duplicat + retry/backoff + recuperare orfane

Inchide bucla de trimitere (plan.md sect. 4 worker, failure registry).

- app/reconcile.py: match_finalizata pe vin+dataPrestatie+odometruFinal (int),
  alege id maxim la duplicate (RAR accepta duplicate, confirmat live)
- app/rar_client.get_finalizate: parseaza data.content (descoperit live ca
  ruta = GET /prezentari/getAllPrezentariFinalizate; filtrele nu merg pe test)
- app/worker rescris:
  - recuperare orfane (rand 'sending' peste lease = worker mort mid-POST)
  - pe eroare tranzitorie/timeout: reconciliere INAINTE de re-send (anti-duplicat);
    daca recordul exista la RAR -> sent fara re-POST
  - retry/backoff exponential; peste worker_max_retries -> error + banner
  - re-login la token expirat (JWT 30h)
- schema: coloana next_attempt_at (backoff) + migrare aditiva in init_db
- config: worker_sending_lease_s, worker_retry_base_s/max_s, worker_max_retries
- contract: documentata ruta+forma getAllPrezentariFinalizate (verificat live)

Verify: pytest 54 passed (15 noi T2) + validare live (reconciliere record 68514).

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

app/db.py

@@ -27,14 +27,22 @@ def get_connection() -> sqlite3.Connection:
 
 
 def init_db() -> None:
-    """Creeaza schema daca lipseste. Idempotent — sigur la fiecare boot."""
+    """Creeaza schema daca lipseste + migrari aditive. Idempotent — sigur la fiecare boot."""
     conn = get_connection()
     try:
         conn.executescript(_SCHEMA.read_text(encoding="utf-8"))
+        _migrate(conn)
     finally:
         conn.close()
 
 
+def _migrate(conn: sqlite3.Connection) -> None:
+    """Migrari aditive pentru DB create inainte de o coloana noua (CREATE IF NOT EXISTS nu altereaza)."""
+    cols = {r["name"] for r in conn.execute("PRAGMA table_info(submissions)").fetchall()}
+    if "next_attempt_at" not in cols:
+        conn.execute("ALTER TABLE submissions ADD COLUMN next_attempt_at TEXT")
+
+
 def _now_iso() -> str:
     return datetime.now(timezone.utc).isoformat(timespec="seconds")