[Bug] quietHours.ts uses UTC time instead of local time — quiet hours are wrong in every timezone #90

Why this matters now: isNowInQuietHours() (line 11) computes now.getUTCHours() * 60 + now.getUTCMinutes() but the user-configured quiet hours (e.g., '22:00' to '07:00') are clearly local times. For a user in Nairobi (UTC+3) who sets quiet hours 22:00-07:00, the function evaluates against UTC, so notifications at 01:00 EAT (22:00 UTC) would be incorrectly suppressed, while notifications at 04:00 EAT (01:00 UTC) would incorrectly fire.

Problem / What: src/utils/quietHours.ts:11 — const nowMin = now.getUTCHours() * 60 + now.getUTCMinutes(). This should use now.getHours() and now.getMinutes() for local time.

Key Challenges:

• Change getUTCHours() / getUTCMinutes() to getHours() / getMinutes().
• Update the existing quietHours.test.ts (if any) to test with timezone offsets.
• The dayKey function in streaks.ts uses local time (getFullYear/getMonth/getDate), which is correct — this inconsistency with quietHours.ts was likely an oversight.
• Consider: should quiet hours be stored as UTC offsets or local time strings? The current approach (local time strings) is more user-friendly.

Acceptance Criteria:

• isNowInQuietHours uses local time (getHours()/getMinutes()).
• Tests verify correct behavior for UTC+0, UTC+3, UTC-5 timezones.
• Quiet hours 22:00-07:00 correctly suppresses notifications at midnight local time in all timezones.
• No other time-related functions use UTC inconsistently.

Relevant files/functions:

• src/utils/quietHours.ts:11
• src/__tests__/ (quietHours test, update or create)

Out of scope: Timezone-aware DST handling.

Labels: bug, intermediate, notifications