Kaia Counter v0.5.1-fix2

Crash fix:
- Removed the undeclared Kaia_Counter_Test::DISPLAY_DIGITS reference.
- Uses an explicit 8-digit display width for the in-house KaiaSpec variant.

State fix:
- Initial display now checks this visitor's own issued-number history.
- No issued number -> KaiaSpec.
- Issued number -> that visitor's own 8-digit number.
- Existing counter/history data is preserved; no reset required.

Plugin identity preserved:
kaia-counter-test/kaia-counter-test.php
