fix(timezone): support half-hour and 45-minute timezone offsets

Critical regression fix for convertTimezoneToOffsetStr:

Issues Fixed:
- Previous regex /^([+-]?\d{1,2}):00/ only matched :00 offsets
- This caused half-hour offsets (e.g., India +05:30) to return UTC+0
- Even if matched, parseInt only parsed hours, losing minute info

Changes:
- Update regex to /^([+-]?\d{1,2}):(\d{2})/ to match all offset formats
- Parse both hours and minutes separately
- Output format: "UTC+5:30" for non-zero minutes, "UTC+8" for whole hours
- Preserve leading zeros in minute part (e.g., "UTC+5:30" not "UTC+5:3")

Test Coverage:
- Added 8 comprehensive tests covering:
  * Default/invalid timezone handling
  * Whole hour offsets (positive/negative)
  * Zero offset (UTC)
  * Half-hour offsets (India +5:30, Australia +9:30)
  * 45-minute offset (Chatham +12:45)
  * Leading zero preservation in minutes

All 14 tests passing. Verified with timezone.json entries at lines 967, 1135, 1251.

web/app/components/base/date-and-time-picker/utils/dayjs.spec.ts

@@ -1,5 +1,6 @@
 import dayjs from './dayjs'
 import {
+  convertTimezoneToOffsetStr,
   getDateWithTimezone,
   isDayjsObject,
   toDayjs,
@@ -65,3 +66,50 @@ describe('dayjs utilities', () => {
     expect(result?.minute()).toBe(0)
   })
 })
+
+describe('convertTimezoneToOffsetStr', () => {
+  test('should return default UTC+0 for undefined timezone', () => {
+    expect(convertTimezoneToOffsetStr(undefined)).toBe('UTC+0')
+  })
+
+  test('should return default UTC+0 for invalid timezone', () => {
+    expect(convertTimezoneToOffsetStr('Invalid/Timezone')).toBe('UTC+0')
+  })
+
+  test('should handle whole hour positive offsets without leading zeros', () => {
+    expect(convertTimezoneToOffsetStr('Asia/Shanghai')).toBe('UTC+8')
+    expect(convertTimezoneToOffsetStr('Pacific/Auckland')).toBe('UTC+12')
+    expect(convertTimezoneToOffsetStr('Pacific/Apia')).toBe('UTC+13')
+  })
+
+  test('should handle whole hour negative offsets without leading zeros', () => {
+    expect(convertTimezoneToOffsetStr('Pacific/Niue')).toBe('UTC-11')
+    expect(convertTimezoneToOffsetStr('Pacific/Honolulu')).toBe('UTC-10')
+    expect(convertTimezoneToOffsetStr('America/New_York')).toBe('UTC-5')
+  })
+
+  test('should handle zero offset', () => {
+    expect(convertTimezoneToOffsetStr('Europe/London')).toBe('UTC+0')
+    expect(convertTimezoneToOffsetStr('UTC')).toBe('UTC+0')
+  })
+
+  test('should handle half-hour offsets (30 minutes)', () => {
+    // India Standard Time: UTC+5:30
+    expect(convertTimezoneToOffsetStr('Asia/Kolkata')).toBe('UTC+5:30')
+    // Australian Central Time: UTC+9:30
+    expect(convertTimezoneToOffsetStr('Australia/Adelaide')).toBe('UTC+9:30')
+    expect(convertTimezoneToOffsetStr('Australia/Darwin')).toBe('UTC+9:30')
+  })
+
+  test('should handle 45-minute offsets', () => {
+    // Chatham Time: UTC+12:45
+    expect(convertTimezoneToOffsetStr('Pacific/Chatham')).toBe('UTC+12:45')
+  })
+
+  test('should preserve leading zeros in minute part for non-zero minutes', () => {
+    // Ensure +05:30 is displayed as "UTC+5:30", not "UTC+5:3"
+    const result = convertTimezoneToOffsetStr('Asia/Kolkata')
+    expect(result).toMatch(/UTC[+-]\d+:30/)
+    expect(result).not.toMatch(/UTC[+-]\d+:3[^0]/)
+  })
+})

web/app/components/base/date-and-time-picker/utils/dayjs.ts

@@ -107,15 +107,18 @@ export const convertTimezoneToOffsetStr = (timezone?: string) => {
   const tzItem = tz.find(item => item.value === timezone)
   if (!tzItem)
     return DEFAULT_OFFSET_STR
-  // Extract offset from name format like "-11:00 Niue Time - Alofi"
-  // Name format is always "{offset}:00 {timezone name}"
-  const offsetMatch = tzItem.name.match(/^([+-]?\d{1,2}):00/)
+  // Extract offset from name format like "-11:00 Niue Time" or "+05:30 India Time"
+  // Name format is always "{offset}:{minutes} {timezone name}"
+  const offsetMatch = tzItem.name.match(/^([+-]?\d{1,2}):(\d{2})/)
   if (!offsetMatch)
     return DEFAULT_OFFSET_STR
-  // Parse offset as integer to remove leading zeros (e.g., "-05" → "-5")
-  const offsetNum = Number.parseInt(offsetMatch[1], 10)
-  const sign = offsetNum >= 0 ? '+' : ''
-  return `UTC${sign}${offsetNum}`
+  // Parse hours and minutes separately
+  const hours = Number.parseInt(offsetMatch[1], 10)
+  const minutes = Number.parseInt(offsetMatch[2], 10)
+  const sign = hours >= 0 ? '+' : ''
+  // If minutes are non-zero, include them in the output (e.g., "UTC+5:30")
+  // Otherwise, only show hours (e.g., "UTC+8")
+  return minutes !== 0 ? `UTC${sign}${hours}:${offsetMatch[2]}` : `UTC${sign}${hours}`
 }
 
 export const isDayjsObject = (value: unknown): value is Dayjs => dayjs.isDayjs(value)