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, 4 insertions, 6 deletions

diff --git a/internal/handlers/timeline.go b/internal/handlers/timeline.go
index ce0e831..9821452 100644
--- a/internal/handlers/timeline.go
+++ b/internal/handlers/timeline.go
@@ -5,6 +5,7 @@ import (
 	"strconv"
 	"time"
 
+	"task-dashboard/internal/config"
 	"task-dashboard/internal/models"
 )
 
@@ -25,19 +26,16 @@ func (h *Handler) HandleTimeline(w http.ResponseWriter, r *http.Request) {
 
 	var start time.Time
 	if startStr != "" {
-		parsed, err := time.ParseInLocation("2006-01-02", startStr, time.Local)
+		parsed, err := config.ParseDateInDisplayTZ(startStr)
 		if err == nil {
 			start = parsed
 		} else {
-			start = time.Now()
+			start = config.Today()
 		}
 	} else {
-		start = time.Now()
+		start = config.Today()
 	}
 
-	// Normalize start to beginning of day
-	start = time.Date(start.Year(), start.Month(), start.Day(), 0, 0, 0, 0, start.Location())
-
 	days := 3 // Default
 	if daysStr != "" {
 		if d, err := strconv.Atoi(daysStr); err == nil && d > 0 {