Function formatLakh

Formats a numeric amount using Pakistani lakh/crore conventions.

• Amounts of 1 crore or more render as "N Crore" (e.g. 10000000 → "1 Crore")
• Amounts of 1 lakh or more render as "N Lakh" (e.g. 2500000 → "25 Lakh")
• Smaller amounts fall back to formatPKR

Values are rounded to two decimals before the unit is chosen, so 9999999 renders as "1 Crore" rather than "100 Lakh". Negative amounts are prefixed with -.