Function isValidLandline

isValidLandline(phone: unknown): boolean
Validates whether the input is a valid Sri Lankan fixed/landline phone number.
Parameters
- phone: unknown
  Phone number to check.
Returns boolean
true only for fixed-line numbers with a known area code.
Example
```
isValidLandline('0112345678'); // true
isValidLandline('0771234567'); // false
```
- Defined in phone/validator.ts:70