feat(account): CLI lifecycle conturi + accounts.active (PRD 3.1)

Inlocuieste crearea conturilor prin INSERT SQL manual cu un tool admin
dedicat, simetric cu tools/apikey.py. Fundatia Etapei 3 (3.2/3.3).

- app/accounts.py: create_account/set_active/list_accounts (helper pur,
  partajat CLI + viitor flux web 3.3). Normalizeaza CUI (trim+upper),
  prinde IntegrityError -> ValueError cu cauza+fix.
- accounts.active (lifecycle cont) + index unic partial ux_accounts_cui
  (unicitate la nivel de index, fara fereastra de coliziune). Migrare
  idempotenta in _migrate.
- tools/account.py: create (--name/--cui/--inactive/--with-key atomic),
  list [--pending], activate/deactivate --account N. Erori -> exit 2.
- 20 teste noi (12 helper + 8 CLI); suita 299 passed.

active e inert pana la gate-ul worker din 3.3 (documentat).

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

app/db.py

@@ -60,6 +60,13 @@ def _migrate(conn: sqlite3.Connection) -> None:
     acc_cols = {r["name"] for r in conn.execute("PRAGMA table_info(accounts)").fetchall()}
     if "rar_creds_enc" not in acc_cols:
         conn.execute("ALTER TABLE accounts ADD COLUMN rar_creds_enc TEXT")
+    if "active" not in acc_cols:
+        # Conturi existente raman active (default 1). Lifecycle consumat de 3.3.
+        conn.execute("ALTER TABLE accounts ADD COLUMN active INTEGER NOT NULL DEFAULT 1")
+    # Unicitate CUI (un CUI = un cont); NULL distinct nativ -> conturi fara CUI multiplu.
+    conn.execute(
+        "CREATE UNIQUE INDEX IF NOT EXISTS ux_accounts_cui ON accounts(cui) WHERE cui IS NOT NULL"
+    )
 
     # Index batch_id pe submissions (poate lipsi pe DB veche)
     existing_idx = {r["name"] for r in conn.execute(