Fix BASE_URL config loading, add tasks/projects; robust .env path resolution

- Config: try ENV_FILE, .env, ../.env for loading; trim trailing slash from BaseURL
- Log BASE_URL at server startup for verification
- .env.example: document BASE_URL
- Tasks, projects, tags, migrations and related API/handlers

Made-with: Cursor

internal/repository/calendars.sql.go

@@ -199,7 +199,7 @@ SELECT c.id, c.owner_id, c.name, c.color, c.is_public, c.count_for_availability,
 FROM calendars c
 JOIN calendar_members cm ON cm.calendar_id = c.id
 WHERE cm.user_id = $1 AND c.deleted_at IS NULL
-ORDER BY c.created_at ASC
+ORDER BY c.sort_order ASC, c.created_at ASC
 `
 
 type ListCalendarsByUserRow struct {