# Multi-Account Filter for Account Balances Report

## Goal
Change the Account Balance report's single-account filter to accept multiple accounts via comma-separated input.

## Current State
- Single `<input type="number">` for account filter (id: `input-account`)
- JS treats `account` as `null` (all accounts) or a single integer
- SQL builders use `AND account = ${account}` equality clause
- Subtitle shows "Account N" or "All accounts"
- CSV filename uses single account value
- Transaction table hides account column when single account is selected

## Tasks

### Task 1: Update HTML — replace single account input with comma-separated text input
**File:** `clientreports/account-balances/index.html`

- Change `<input type="number" id="input-account">` to `<input type="text" id="input-accounts">`
- Update label text from "Account" to "Accounts"
- Update placeholder: "e.g. 12345, 67890" 
- Update hint text to "(blank = all)"
- Error element id stays as `account-error`

### Task 2: Update JavaScript — parse multiple accounts, update SQL builders, validation, and all references
**File:** `clientreports/account-balances/account-balances.js`

#### Parse function
- Add `parseAccounts(raw)` function that:
  - Returns `null` for empty string (meaning "all accounts")
  - Splits on commas, trims each value, parses as integer
  - Filters out invalid values, returns array of unique positive integers
  - Returns empty array `[]` if all values are invalid (treated as error)

#### Validation (`validateInputs`)
- Update to read `input-accounts` instead of `input-account`
- Validate each entry is a positive integer
- Show error listing invalid entries

#### SQL builders (`buildDailyNetSql`, `buildTxnsSql`)
- Change signature: `account` param becomes `accounts` (null | number[])
- When `accounts` is `null`: no clause (all accounts)
- When `accounts` is non-empty array: `AND account IN (${accounts.join(', ')})`
- Keep existing behavior otherwise

#### Generate function
- Parse accounts from input: `const accounts = parseAccounts(document.getElementById('input-accounts').value.trim())`
- Pass `accounts` (array or null) to SQL builders
- Subtitle: `accounts !== null ? \`Accounts ${accounts.join(', ')}\` : 'All accounts'`

#### State
- Update `_ctx` to store `accounts` instead of `account`

#### Report subtitle
- Use accounts array for display

#### CSV download
- Filename: use joined accounts or "all"

#### Transaction table
- When multiple accounts selected: show account column (`accounts === null || accounts.length > 1`)

#### Empty state message
- Update "Account N — no data" to use accounts display string

## Verification
- Commit after each task completes and passes review
- SQL output in browser console should show correct IN clause
- All accounts works when input is blank