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, 82 insertions, 0 deletions

diff --git a/TIMELINE_DESIGN.md b/TIMELINE_DESIGN.md
new file mode 100644
index 0000000..61c71b5
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+++ b/TIMELINE_DESIGN.md
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+# Timeline Feature Design
+
+## Objective
+Create a unified timeline view showing Tasks, Meals, Trello Cards, and Google Calendar Events, sorted chronologically.
+
+## Data Sources
+1.  **Tasks (Todoist):** From DB `tasks` table. Filter: `due_date` is not null.
+2.  **Meals (PlanToEat):** From DB `meals` table. Filter: `date` is not null.
+3.  **Cards (Trello):** From DB `cards` table. Filter: `due_date` is not null.
+4.  **Google Calendar Events:** From `GoogleCalendarClient` (Live API).
+
+## Backend Logic
+
+### 1. Data Models (`internal/models/timeline.go`)
+We need a polymorphic structure to hold different item types.
+
+```go
+type TimelineItemType string
+
+const (
+    ItemTypeTask  TimelineItemType = "task"
+    ItemTypeMeal  TimelineItemType = "meal"
+    ItemTypeCard  TimelineItemType = "card"
+    ItemTypeEvent TimelineItemType = "event"
+)
+
+type TimelineItem struct {
+    ID          string           `json:"id"`
+    Type        TimelineItemType `json:"type"`
+    Title       string           `json:"title"`
+    Description string           `json:"description"`
+    Time        time.Time        `json:"time"`
+    AllDay      bool             `json:"all_day"`
+    URL         string           `json:"url"`
+    Meta        map[string]any   `json:"meta"` // Extra data like ProjectName, RecipeURL, etc.
+}
+```
+
+### 2. Store Extensions (`internal/store/`)
+Add methods to fetch items by date range.
+*   `GetTasksByDateRange(start, end time.Time) ([]models.Task, error)`
+*   `GetMealsByDateRange(start, end time.Time) ([]models.Meal, error)`
+*   `GetCardsByDateRange(start, end time.Time) ([]models.Card, error)`
+
+### 3. Logic Layer (`internal/handlers/timeline_logic.go`)
+*   **Function:** `BuildTimeline(store Store, calendarClient *api.GoogleCalendarClient, start, end time.Time) ([]TimelineItem, error)`
+*   **Aggregation:**
+    1.  Fetch from Store (Tasks, Meals, Cards).
+    2.  Fetch from Calendar API.
+    3.  Convert all to `TimelineItem`.
+    4.  **Meal Time Defaults:**
+        *   Breakfast: 08:00
+        *   Lunch: 12:00
+        *   Dinner: 19:00
+        *   Other: 12:00
+    5.  Sort by `Time`.
+
+### 4. HTTP Handler (`internal/handlers/timeline.go`)
+*   **Route:** `GET /timeline`
+*   **Params:** `start` (default: today), `days` (default: 7)
+*   **Response:** Render `timeline-tab.html` partial.
+
+## UI Design (`web/templates/partials/timeline-tab.html`)
+*   **Structure:**
+    *   Container
+    *   Loop through Days
+        *   Date Header (e.g., "Mon, Jan 2")
+        *   List of Items
+            *   Time Column (e.g., "14:00")
+            *   Content Column (Icon + Title + Subtitle)
+*   **Styling:**
+    *   Use existing CSS variables.
+    *   Distinct icons/colors for Tasks vs Meals vs Events.
+
+## Files to Modify
+1.  `internal/models/timeline.go` (New)
+2.  `internal/store/store.go` (Interface update)
+3.  `internal/store/sqlite.go` (Implementation update)
+4.  `internal/handlers/timeline_logic.go` (New)
+5.  `internal/handlers/timeline.go` (New)
+6.  `web/templates/partials/timeline-tab.html` (New)
+7.  `cmd/dashboard/main.go` (Route registration)