fix(ui): restore login primary action hierarchy

[Jdelg718]

Problem

The unloaded login menu intends Load Mnemonic and New Mnemonic to use the orange primary-action style, with Scan and Settings visually secondary.

That hierarchy originally worked when the menu contained Load, New, and Settings. Commit 96d1628 later inserted Scan at index 0, but the positional for (i = 2; ...) styling cutoff was not updated. The idle menu therefore showed Scan + Load as primary and New + Settings as secondary.

Change

• Mark Scan secondary immediately after its entry is successfully created.
• Leave Load Mnemonic and New Mnemonic at the menu's default primary style.
• Mark Settings secondary immediately after its entry is successfully created.
• Remove the fragile range-based positional cutoff.
• Guard each style assignment with the corresponding successful entry creation so an insertion failure cannot recolor a preceding item.

Result

Idle unloaded-menu hierarchy:

• Scan — secondary
• Load Mnemonic — primary
• New Mnemonic — primary
• Settings — secondary

Entry order, labels, icons, callbacks, geometry, touch behavior, global theme semantics, and wallet/security logic are unchanged.

Verification

• Independent source probe reproduced the old hierarchy and passes after the fix.
• Exact staged block compiled with stubs and passed all Scan/Settings insertion success/failure combinations.
• Changed file passes clang-format --dry-run --Werror.
• git diff --check passes.
• Independent review and exact-index review passed.
• Upstream CI will provide the canonical Linux tests and all-board firmware build matrix.

Scope

This is intentionally separate from #152. It is a small pre-existing visual hierarchy regression observed during physical wave_43 validation and has no security impact.