Add regional task templates API with climate zone lookup

Adds a new endpoint GET /api/tasks/templates/by-region/?zip= that resolves
ZIP codes to IECC climate regions and returns relevant home maintenance
task templates. Includes climate region model, region lookup service with
tests, seed data for all 8 climate zones with 50+ templates, and OpenAPI spec.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/repositories/task_template_repo.go

@@ -104,6 +104,20 @@ func (r *TaskTemplateRepository) Count() (int64, error) {
 	return count, err
 }
 
+// GetByRegion returns active templates associated with a specific climate region
+func (r *TaskTemplateRepository) GetByRegion(regionID uint) ([]models.TaskTemplate, error) {
+	var templates []models.TaskTemplate
+	err := r.db.
+		Preload("Category").
+		Preload("Frequency").
+		Preload("Regions").
+		Joins("JOIN task_tasktemplate_regions ON task_tasktemplate_regions.task_template_id = task_tasktemplate.id").
+		Where("task_tasktemplate_regions.climate_region_id = ? AND task_tasktemplate.is_active = ?", regionID, true).
+		Order("task_tasktemplate.display_order ASC, task_tasktemplate.title ASC").
+		Find(&templates).Error
+	return templates, err
+}
+
 // GetGroupedByCategory returns templates grouped by category name
 func (r *TaskTemplateRepository) GetGroupedByCategory() (map[string][]models.TaskTemplate, error) {
 	templates, err := r.GetAll()