feat(v2): multi-tranche DB schema + gate cumulativo 5 voci Cecilia

A1 migrations.py:
- remission_practice DROP uq_application + ADD sequence_number/period_label/suggested_instructor_id
- UNIQUE composita (application_id, sequence_number)
- partial index idx_remission_practice_unassigned su assigned_instructor_id NULL
- nuova tabella remission_custom_check_value (storage_path/mime/size/sha256 allineata adapter)

A2 models.py + templates.py:
- RemissionPractice: UniqueConstraint composita, campi multi-tranche, relationship custom_checks
- classe RemissionCustomCheckValue
- RESTART_TEMPLATE schema_version=2, max_tranches=2, custom_checks esempio
  (antiriciclaggio required no-doc, polizza_fidejussoria optional con-doc)
- upgrade_schema_to_v2 idempotente per snapshot v1 esistenti

A3 _compute_gate_check(db, practice) CUMULATIVO:
- max_remission_global = min(cap_pct * erogato, cap_abs)
- already_approved = func.sum(approved_remission) su tranche APPROVED precedenti
  dello stesso application_id con sequence_number < corrente
- max_remission_this_tranche = max(0, global - already_approved)
- pre_check_admissible = min(grand_total_declared, this_tranche)  [voce 2 Cecilia]
- remission_due = min(effective_total, this_tranche)
- residuo_da_restituire = erogato - already_approved - remission_due (cumulativo)
- output totals esteso: sequence_number, tranches_count, tranches_max
- signature (db, practice) - aggiornati 6 call site in practices/instructor/verbale

Test su NAPOLI SAS: erogato 17K, cap 8500, tranche 1 approvata 467.14EUR,
tranche 2 vuota -> residuo disponibile 8032.86EUR, residuo_da_restituire 16532.86EUR.

app/schemas.py

@@ -40,8 +40,10 @@ class RemissionSchemaOut(BaseModel):
 # ====================== Pratica di rendicontazione (beneficiario) ======================
 
 class PracticeStartRequest(BaseModel):
-    """Input minimo per avviare una pratica: solo application_id. Il resto viene dal DB."""
+    """Input per avviare una (nuova) pratica o tranche."""
     application_id: int
+    period_label: Optional[str] = None  # es "I trimestre 2021" — libero
+    copy_ula_from_previous: bool = True  # ignorato se e la prima tranche
 
 
 class PracticeUpdate(BaseModel):
@@ -160,6 +162,11 @@ class PracticeOut(BaseModel):
     instructor_checklist: Optional[dict] = None
     verbale_date: Optional[date] = None
 
+    # v2 multi-tranche
+    sequence_number: int = 1
+    period_label: Optional[str] = None
+    suggested_instructor_id: Optional[int] = None
+
     invoices: List[InvoiceOut] = []
     ula_employees: List[UlaEmployeeOut] = []
     documents: List[DocumentOut] = []
@@ -178,6 +185,11 @@ class PracticeListItem(BaseModel):
     created_at: datetime
     submitted_at: Optional[datetime] = None
 
+    # v2 multi-tranche
+    sequence_number: int = 1
+    period_label: Optional[str] = None
+    suggested_instructor_id: Optional[int] = None
+
     # campi denormalizzati aggiunti a runtime
     call_name: Optional[str] = None
     company_name: Optional[str] = None
@@ -237,6 +249,9 @@ class InstructorQueueItem(BaseModel):
     id: UUID
     call_id: int
     application_id: int
+    sequence_number: int = 1
+    period_label: Optional[str] = None
+    suggested_instructor_id: Optional[int] = None
     company_id: int
     status: str
     amount_erogato: Decimal
@@ -288,3 +303,76 @@ class ApiResponse(BaseModel):
     status: str = "SUCCESS"
     message: Optional[str] = None
     data: Optional[Any] = None
+
+
+# ====================== v2 Custom checks ======================
+
+class CustomCheckDeclareBody(BaseModel):
+    beneficiary_declared: bool
+
+
+class CustomCheckVerifyBody(BaseModel):
+    verification_status: str  # PENDING | VALIDO | NON_VALIDO
+    verification_notes: Optional[str] = None
+
+
+class CustomCheckOut(BaseModel):
+    """Vista merged di definition (da schema) + value (dal DB)."""
+    code: str
+    label: str
+    description: Optional[str] = None
+    requires_document: bool = False
+    required: bool = False
+    # valori
+    beneficiary_declared: bool = False
+    declared_at: Optional[datetime] = None
+    filename_original: Optional[str] = None
+    storage_path: Optional[str] = None
+    size_bytes: Optional[int] = None
+    document_uploaded_at: Optional[datetime] = None
+    verification_status: str = "PENDING"
+    verification_notes: Optional[str] = None
+    verified_by: Optional[int] = None
+    verified_at: Optional[datetime] = None
+
+
+# ====================== v2 Reassign istruttore ======================
+
+class PracticeReassignBody(BaseModel):
+    new_instructor_id: Optional[int] = None  # None = unassign ritorno in coda
+    reassignment_reason: Optional[str] = None
+
+
+# ====================== v2 Tranches ======================
+
+class ApplicationTranchesSummary(BaseModel):
+    """Riepilogo pratiche/tranche per una application."""
+    application_id: int
+    call_id: int
+    call_name: Optional[str] = None
+    company_id: int
+    company_name: Optional[str] = None
+    amount_erogato: float
+    max_tranches: int = 1
+    # summary tranche esistenti
+    tranches: List[PracticeListItem] = []
+    # stato apertura nuova tranche
+    can_start_new: bool = False
+    start_blocked_reason: Optional[str] = None
+    # importi cumulativi
+    already_approved_sum: float = 0
+    max_remission_global: float = 0
+    max_remission_next_tranche: float = 0
+
+
+class CopyUlaOption(BaseModel):
+    """Dipendente copiabile da tranche precedente."""
+    codice_fiscale: str
+    full_name: str
+    contract_type: str
+    role_description: Optional[str] = None
+    fte_pct: float
+    period_start_date: date
+    period_end_date: date
+    supporting_doc_type: Optional[str] = None
+