Function is_fingerprint_available 

pub fn is_fingerprint_available() -> bool

What: Check whether fingerprint authentication appears to be available.

Inputs:

• None (uses the active privilege tool from settings).

Output:

• true if both PAM fingerprint integration and an enrolled finger are detected.

Details:

• Result is cached for the lifetime of the process (checked once, never re-checked).
• Requires both pam_fprintd in the tool’s PAM stack AND at least one enrolled finger.
• Informational only — used to show a hint in the password modal, never gates execution.