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/models/climate_region.go

@@ -0,0 +1,28 @@
+package models
+
+// ClimateRegion represents an IECC climate zone for regional task templates
+type ClimateRegion struct {
+	BaseModel
+	Name        string `gorm:"column:name;size:100;not null;uniqueIndex" json:"name"`
+	ZoneNumber  int    `gorm:"column:zone_number;not null;index" json:"zone_number"`
+	Description string `gorm:"column:description;type:text" json:"description"`
+	IsActive    bool   `gorm:"column:is_active;default:true;index" json:"is_active"`
+}
+
+// TableName returns the table name for GORM
+func (ClimateRegion) TableName() string {
+	return "task_climateregion"
+}
+
+// ZipClimateRegion maps ZIP codes to climate regions (static lookup)
+type ZipClimateRegion struct {
+	BaseModel
+	ZipCode         string        `gorm:"column:zip_code;size:10;uniqueIndex;not null" json:"zip_code"`
+	ClimateRegionID uint          `gorm:"column:climate_region_id;index;not null" json:"climate_region_id"`
+	ClimateRegion   ClimateRegion `gorm:"foreignKey:ClimateRegionID" json:"climate_region,omitempty"`
+}
+
+// TableName returns the table name for GORM
+func (ZipClimateRegion) TableName() string {
+	return "task_zipclimateregion"
+}

internal/models/task_template.go

@@ -13,7 +13,8 @@ type TaskTemplate struct {
 	IconAndroid     string        `gorm:"column:icon_android;size:100" json:"icon_android"`
 	Tags            string        `gorm:"column:tags;type:text" json:"tags"` // Comma-separated tags for search
 	DisplayOrder    int           `gorm:"column:display_order;default:0" json:"display_order"`
-	IsActive        bool          `gorm:"column:is_active;default:true;index" json:"is_active"`
+	IsActive        bool            `gorm:"column:is_active;default:true;index" json:"is_active"`
+	Regions         []ClimateRegion `gorm:"many2many:task_tasktemplate_regions;" json:"regions,omitempty"`
 }
 
 // TableName returns the table name for GORM