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, 8 insertions, 4 deletions

diff --git a/internal/models/atom.go b/internal/models/atom.go
index 3e08896..3804de4 100644
--- a/internal/models/atom.go
+++ b/internal/models/atom.go
@@ -3,6 +3,8 @@ package models
 import (
 	"fmt"
 	"time"
+
+	"task-dashboard/internal/config"
 )
 
 type AtomSource string
@@ -56,19 +58,21 @@ func (a *Atom) ComputeUIFields() {
 		return
 	}
 
-	now := time.Now()
-	today := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, now.Location())
+	tz := config.GetDisplayTimezone()
+	now := config.Now()
+	today := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, tz)
 	tomorrow := today.AddDate(0, 0, 1)
 
 	// Check if overdue (due date is before today)
-	dueDay := time.Date(a.DueDate.Year(), a.DueDate.Month(), a.DueDate.Day(), 0, 0, 0, 0, a.DueDate.Location())
+	dueInTZ := a.DueDate.In(tz)
+	dueDay := time.Date(dueInTZ.Year(), dueInTZ.Month(), dueInTZ.Day(), 0, 0, 0, 0, tz)
 	a.IsOverdue = dueDay.Before(today)
 
 	// Check if future (due date is after today)
 	a.IsFuture = !dueDay.Before(tomorrow)
 
 	// Check if has set time (not midnight)
-	a.HasSetTime = a.DueDate.Hour() != 0 || a.DueDate.Minute() != 0
+	a.HasSetTime = dueInTZ.Hour() != 0 || dueInTZ.Minute() != 0
 }
 
 // TaskToAtom converts a Todoist Task to an Atom