feat: endpoint istruttore (queue + review + soccorso istruttorio)

- 4 nuove colonne su remission_practice: assigned_instructor_id, reviewed_at,
  reviewed_by, rejection_reason, approved_remission
- Nuova tabella remission_amendment_request con cascade delete, scope JSONB,
  stati AWAITING -> RESPONSE_RECEIVED -> CLOSED / EXPIRED / REJECTED
- Router instructor.py (287 righe) con 8 endpoint:
  /queue, /{id}, /{id}/claim, /{id}/approve, /{id}/reject,
  /{id}/amendment, /{id}/amendment/{aid}/close,
  /{id}/amendment/{aid}/respond-beneficiary
- GET /{id} (router practices) ora include amendments nel payload
- Manager manager_view flag per ROLE_INSTRUCTOR_MANAGER + SUPER_ADMIN
  (vede tutto il pool vs solo le proprie assegnazioni)
- Logica status transitions verificata:
  SUBMITTED -> UNDER_REVIEW (claim)
  UNDER_REVIEW <-> AWAITING_AMENDMENT (amendment open/close)
  UNDER_REVIEW | AWAITING_AMENDMENT -> APPROVED | REJECTED
- _compute_gate_check riusato anche dal router istruttore per calcolo
  remission_due in coda e nel dettaglio

Test end-to-end verde: ciclo completo benef -> istruttore -> soccorso ->
risposta -> chiusura -> approvazione funzionante su NAPOLI SAS.

app/schemas.py

@@ -165,6 +165,64 @@ class GateCheckResult(BaseModel):
     totals: dict        # {per_category: {B1: 1234.56, ...}, grand_total, max_remission_due, ...}
 
 
+# ====================== Istruttoria ======================
+
+class AmendmentRequestCreate(BaseModel):
+    request_text: str
+    deadline: date
+    scope: Optional[dict] = None
+
+
+class AmendmentResponseSubmit(BaseModel):
+    response_text: str
+
+
+class AmendmentRequestOut(BaseModel):
+    id: UUID
+    practice_id: UUID
+    requested_by: int
+    request_text: str
+    scope: Optional[dict] = None
+    deadline: date
+    status: str
+    response_text: Optional[str] = None
+    response_at: Optional[datetime] = None
+    closed_at: Optional[datetime] = None
+    closed_by: Optional[int] = None
+    created_at: datetime
+
+    model_config = {"from_attributes": True}
+
+
+class ReviewRejectBody(BaseModel):
+    rejection_reason: str
+
+
+class ReviewApproveBody(BaseModel):
+    approved_remission: Optional[Decimal] = None
+    notes: Optional[str] = None
+
+
+class InstructorQueueItem(BaseModel):
+    id: UUID
+    call_id: int
+    application_id: int
+    company_id: int
+    status: str
+    amount_erogato: Decimal
+    submitted_at: Optional[datetime] = None
+    assigned_instructor_id: Optional[int] = None
+    call_name: Optional[str] = None
+    company_name: Optional[str] = None
+    invoice_count: int = 0
+    ula_count: int = 0
+    document_count: int = 0
+    open_amendments: int = 0
+    remission_due: Optional[float] = None
+
+    model_config = {"from_attributes": True}
+
+
 # ====================== Wrapper ======================
 
 class ApiResponse(BaseModel):