fix(desktop): generic monthly-limit popup copy for menu-bar trigger

[mdmohsin7]

Summary

• Menu-bar Screen Capture / Audio Recording toggles in OmiApp.swift:1033, 1070 post showUsageLimitPopup with reason: "trial_expired". That string fell through to the default branch of UsageLimitPopupView.body_text and returned the same copy as the transcription-cap case: "Upgrade to make sure your new recordings aren't lost."
• That phrasing reads as a data-loss threat. For users tripping the stale desktop_isPaywalled flag (now self-healed at launch by desktop: clear sticky paywalled flag on launch for paid-plan users (follow-up to #7514) #7517) while also at their Neo chat cap, listening was never actually paywalled server-side — but the copy made them believe their recordings were at risk.
• Switches the default branch to plan-agnostic copy: "Upgrade to keep using Omi without restrictions." The explicit "transcription" case is unchanged (real transcription-cap → recordings copy is accurate).

Why now

Surfaced while investigating the same Neo grandfathered cohort #7517 fixed at launch. Several users on legacy Unlimited / Neo plans were seeing the recordings-loss copy on the menu-bar toggle path while their backend state correctly reported trial_expired=false and chat_quota_allowed=true. After #7517 self-heals the stale flag on next launch, this popup should no longer fire for them in normal flow — but the copy bug also affects any legitimate "trial_expired" paywall (basic trial expired with no BYOK), where the same data-loss framing is inaccurate.

Test plan

• Build via Codemagic (no local Swift toolchain on this CI host)
• Manual: menu-bar Screen Capture toggle while isPaywalled=true → popup body reads "Upgrade to keep using Omi without restrictions."
• Manual: hit transcription cap → popup body still reads "…new recordings aren't lost."
• Manual: hit chat cap → popup body still reads "…keep chatting with Omi without restrictions."

🤖 Generated with Claude Code