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>

3 files changed, 12 insertions, 15 deletions

diff --git a/internal/handlers/handlers.go b/internal/handlers/handlers.go
index 595ab67..1e376b5 100644
--- a/internal/handlers/handlers.go
+++ b/internal/handlers/handlers.go
@@ -124,7 +124,7 @@ func (h *Handler) HandleGetTasks(w http.ResponseWriter, r *http.Request) {
 
 // HandleGetMeals returns meals as JSON
 func (h *Handler) HandleGetMeals(w http.ResponseWriter, r *http.Request) {
-	startDate := time.Now()
+	startDate := config.Now()
 	endDate := startDate.AddDate(0, 0, 7)
 
 	meals, err := h.store.GetMeals(startDate, endDate)
@@ -183,7 +183,7 @@ func (h *Handler) HandleRefreshTab(w http.ResponseWriter, r *http.Request) {
 // aggregateData fetches and caches data from all sources concurrently
 func (h *Handler) aggregateData(ctx context.Context, forceRefresh bool) (*models.DashboardData, error) {
 	data := &models.DashboardData{
-		LastUpdated: time.Now(),
+		LastUpdated: config.Now(),
 		Errors:      make([]string, 0),
 	}
 
@@ -423,7 +423,7 @@ func (h *Handler) convertSyncItemToTask(item api.SyncItemResponse, projectMap ma
 
 // fetchMeals fetches meals from cache or API
 func (h *Handler) fetchMeals(ctx context.Context, forceRefresh bool) ([]models.Meal, error) {
-	startDate := time.Now()
+	startDate := config.Now()
 	endDate := startDate.AddDate(0, 0, 7)
 
 	fetcher := &CacheFetcher[models.Meal]{
@@ -741,7 +741,7 @@ func (h *Handler) HandleUnifiedAdd(w http.ResponseWriter, r *http.Request) {
 
 	var dueDate *time.Time
 	if dueDateStr != "" {
-		if parsed, err := time.ParseInLocation("2006-01-02", dueDateStr, time.Local); err == nil {
+		if parsed, err := config.ParseDateInDisplayTZ(dueDateStr); err == nil {
 			dueDate = &parsed
 		}
 	}
@@ -978,7 +978,7 @@ func (h *Handler) HandleTabTasks(w http.ResponseWriter, r *http.Request) {
 		Atoms:       currentAtoms,
 		FutureAtoms: futureAtoms,
 		Boards:      boards,
-		Today:       time.Now().Format("2006-01-02"),
+		Today:       config.Now().Format("2006-01-02"),
 	}
 
 	HTMLResponse(w, h.templates, "tasks-tab", data)
@@ -986,8 +986,7 @@ func (h *Handler) HandleTabTasks(w http.ResponseWriter, r *http.Request) {
 
 // HandleTabPlanning renders the Planning tab with structured sections
 func (h *Handler) HandleTabPlanning(w http.ResponseWriter, r *http.Request) {
-	now := time.Now()
-	today := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, now.Location())
+	today := config.Today()
 	tomorrow := today.AddDate(0, 0, 1)
 	in3Days := today.AddDate(0, 0, 4)
 
@@ -1121,7 +1120,7 @@ func (h *Handler) HandleTabPlanning(w http.ResponseWriter, r *http.Request) {
 
 // HandleTabMeals renders the Meals tab (PlanToEat)
 func (h *Handler) HandleTabMeals(w http.ResponseWriter, r *http.Request) {
-	startDate := time.Now()
+	startDate := config.Now()
 	endDate := startDate.AddDate(0, 0, 7)
 
 	meals, err := h.store.GetMeals(startDate, endDate)
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 {
diff --git a/internal/handlers/timeline_logic.go b/internal/handlers/timeline_logic.go
index 0d4595f..bead98f 100644
--- a/internal/handlers/timeline_logic.go
+++ b/internal/handlers/timeline_logic.go
@@ -14,7 +14,7 @@ import (
 // BuildTimeline aggregates and normalizes data into a timeline structure
 func BuildTimeline(ctx context.Context, s *store.Store, calendarClient api.GoogleCalendarAPI, start, end time.Time) ([]models.TimelineItem, error) {
 	var items []models.TimelineItem
-	now := time.Now()
+	now := config.Now()
 
 	// 1. Fetch Tasks
 	tasks, err := s.GetTasksByDateRange(start, end)