Use configured timezone throughout codebase

- Add config/timezone.go with timezone utilities:
  - SetDisplayTimezone(), GetDisplayTimezone()
  - Now(), Today() - current time/date in display TZ
  - ParseDateInDisplayTZ(), ToDisplayTZ() - parsing helpers

- Initialize timezone at startup in main.go

- Update all datetime logic to use configured timezone:
  - handlers/handlers.go - all time.Now() calls
  - handlers/timeline.go - date parsing
  - handlers/timeline_logic.go - now calculation
  - models/atom.go - ComputeUIFields()
  - models/timeline.go - ComputeDaySection()
  - api/plantoeat.go - meal date parsing
  - api/todoist.go - due date parsing
  - api/trello.go - due date parsing

This ensures all dates/times display correctly regardless
of server timezone setting.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

1 files changed, 11 insertions, 6 deletions

diff --git a/internal/models/timeline.go b/internal/models/timeline.go
index 54f7f45..3475696 100644
--- a/internal/models/timeline.go
+++ b/internal/models/timeline.go
@@ -1,6 +1,10 @@
 package models
 
-import "time"
+import (
+	"time"
+
+	"task-dashboard/internal/config"
+)
 
 type TimelineItemType string
 
@@ -37,15 +41,16 @@ type TimelineItem struct {
 
 // ComputeDaySection sets the DaySection based on the item's time
 func (item *TimelineItem) ComputeDaySection(now time.Time) {
-	// Ensure we're working in local timezone for consistent comparisons
-	localNow := now.Local()
-	localItemTime := item.Time.Local()
+	// Use configured display timezone for consistent comparisons
+	tz := config.GetDisplayTimezone()
+	localNow := now.In(tz)
+	localItemTime := item.Time.In(tz)
 
-	today := time.Date(localNow.Year(), localNow.Month(), localNow.Day(), 0, 0, 0, 0, time.Local)
+	today := time.Date(localNow.Year(), localNow.Month(), localNow.Day(), 0, 0, 0, 0, tz)
 	tomorrow := today.AddDate(0, 0, 1)
 	dayAfterTomorrow := today.AddDate(0, 0, 2)
 
-	itemDay := time.Date(localItemTime.Year(), localItemTime.Month(), localItemTime.Day(), 0, 0, 0, 0, time.Local)
+	itemDay := time.Date(localItemTime.Year(), localItemTime.Month(), localItemTime.Day(), 0, 0, 0, 0, tz)
 
 	if itemDay.Before(tomorrow) {
 		item.DaySection = DaySectionToday