fix(ui): add-channel dialog buttons are 32 px tall on touch (below the 48 px minimum)

[dborup]

Relates to #235, #239

Problem

The #239 review found that the primary buttons in the add-channel dialog are only 32 px tall on touch devices (measured at 390×844 touch, the same on master):

• #chGenerateBtn: 181×32
• #chPskAddBtn: 67×32
• #chHashtagBtn: 91×32

They were never 44 px, so #235 did not cover them. The house minimum is 48 px (Kpa-clawbot#2052).

Proposed fix

Raise them to at least 48 px tall, using the existing CSS variables or tokens. Check the dialog layout at 390 px and on desktop. Add the buttons to test-touch-targets.js or to the Kpa-clawbot#2052 E2E.

Acceptance

• All three buttons measure at least 48 px tall at mobile width, with no overflow in the dialog.
• A test fails if one of them goes back to 32 px.

[dborup]

Fixed by #264 (merged as a771ca40).