GL account mapping validation

# GL accounting mapping validation

## Purpose
Verify that all payables ready to export have a valid GL code present in the company's chart of accounts. Prevents ERP import rejections caused by missing or invalid codes.

## Instructions

### Step 1 — Retrieve the reference chart of accounts
```
Call get_chart_of_accounts.
Extract the list of valid GL codes: { accountCode, accountType, label }
Build a set of valid codes for validation.
```

### Step 2 — Retrieve the payables to check
```
Call get_payables with bookingStatus=toExport (payables ready to export).
For each payable: retrieve id, amount, supplierId, glCode (or accountingCode),
invoiceDate, payableType.
```

### Step 3 — Check for the presence of the GL code
```
For each payable:
  CASE 1: glCode missing or null → "Missing GL code"
  CASE 2: glCode present but not in the chart of accounts → "Invalid GL code"
  CASE 3: glCode present and in the chart of accounts → OK ✅

Count and list cases 1 and 2.
```

### Step 4 — Enrichment of anomalies
```
For payables with a GL anomaly:
  Resolve the supplier name via get_supplier_by_id (for the top 20)
  Identify the type (invoice, expense claim, subscription) to prioritize the fix
```

### Step 5 — GL validation report
```
Present:
1. Summary: X payables OK | X with no GL code | X with an invalid code
2. List of payables with no GL code (to fix as a priority before export)
3. List of invalid GL codes with the code used vs. suggested valid codes
4. Total amount blocked by GL anomalies
5. Recommendation: block the export until these payables are fixed
```

## Points to watch
- The name of the GL code field may vary depending on the Spendesk configuration (glCode, accountingCode, glAccount)
- A missing GL code = immediate rejection when importing into most ERPs
- Do not export until the anomaly list is at zero

## Example prompts
- "Check that all my payables to export have a valid accounting code"
- "Are there any invoices with no GL code before my close?"
- "Show me the accounting mapping errors in the payables to export this month"