Kaia Counter — Take 3 Final / v0.4.0

Final UI polish:
- Label: SUPPORTER NO.
- Button: GET NUMBER
- During request: GETTING... and short rolling-number animation
- Success: GOT IT! and disabled/greyed button
- Success message below the button is removed; the number + button state show completion
- Digits have a tiny fixed vertical offset per position for a vintage counter feel
- Failure restores the prior displayed number
- Issued-state message remains:
  既に発行されているため、発行できません。
- Internal guard details are not exposed
- Existing DB/current number/history are preserved
- No font files bundled
- PDF generation remains a separate next stage

Shortcode:
[kaia_counter id="counter-test"]
