Onboarding: template backlink, bulk-create endpoint, climate-region scoring

Clients that send users through a multi-task onboarding step no longer
loop N POST /api/tasks/ calls and no longer create "orphan" tasks with
no reference to the TaskTemplate they came from.

Task model
- New task_template_id column + GORM FK (migration 000016)
- CreateTaskRequest.template_id, TaskResponse.template_id
- task_service.CreateTask persists the backlink

Bulk endpoint
- POST /api/tasks/bulk/ — 1-50 tasks in a single transaction,
  returns every created row + TotalSummary. Single residence access
  check, per-entry residence_id is overridden with batch value
- task_handler.BulkCreateTasks + task_service.BulkCreateTasks using
  db.Transaction; task_repo.CreateTx + FindByIDTx helpers

Climate-region scoring
- templateConditions gains ClimateRegionID; suggestion_service scores
  residence.PostalCode -> ZipToState -> GetClimateRegionIDByState against
  the template's conditions JSON (no penalty on mismatch / unknown ZIP)
- regionMatchBonus 0.35, totalProfileFields 14 -> 15
- Standalone GET /api/tasks/templates/by-region/ removed; legacy
  task_tasktemplate_regions many-to-many dropped (migration 000017).
  Region affinity now lives entirely in the template's conditions JSON

Tests
- +11 cases across task_service_test, task_handler_test, suggestion_
  service_test: template_id persistence, bulk rollback + cap + auth,
  region match / mismatch / no-ZIP / unknown-ZIP / stacks-with-others

Docs
- docs/openapi.yaml: /tasks/bulk/ + BulkCreateTasks schemas, template_id
  on TaskResponse + CreateTaskRequest, /templates/by-region/ removed

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

internal/services/suggestion_service.go

@@ -26,7 +26,9 @@ func NewSuggestionService(db *gorm.DB, residenceRepo *repositories.ResidenceRepo
 	}
 }
 
-// templateConditions represents the parsed conditions JSON from a task template
+// templateConditions represents the parsed conditions JSON from a task template.
+// Every field is optional; a template with no conditions is "universal" and
+// receives a small base score. See scoreTemplate for how each field is used.
 type templateConditions struct {
 	HeatingType     *string `json:"heating_type,omitempty"`
 	CoolingType     *string `json:"cooling_type,omitempty"`
@@ -43,6 +45,11 @@ type templateConditions struct {
 	HasBasement     *bool   `json:"has_basement,omitempty"`
 	HasAttic        *bool   `json:"has_attic,omitempty"`
 	PropertyType    *string `json:"property_type,omitempty"`
+	// ClimateRegionID replaces the old task_tasktemplate_regions join table.
+	// Tag a template with the IECC zone ID it's relevant to (e.g. "Winterize
+	// Sprinkler" → zone 5/6). Residence.PostalCode is mapped to a region at
+	// scoring time via ZipToState + GetClimateRegionIDByState.
+	ClimateRegionID *uint `json:"climate_region_id,omitempty"`
 }
 
 // isEmpty returns true if no conditions are set
@@ -52,17 +59,20 @@ func (c *templateConditions) isEmpty() bool {
 		c.LandscapingType == nil && c.HasPool == nil && c.HasSprinkler == nil &&
 		c.HasSeptic == nil && c.HasFireplace == nil && c.HasGarage == nil &&
 		c.HasBasement == nil && c.HasAttic == nil &&
-		c.PropertyType == nil
+		c.PropertyType == nil && c.ClimateRegionID == nil
 }
 
 const (
-	maxSuggestions        = 30
-	baseUniversalScore    = 0.3
-	stringMatchBonus      = 0.25
-	boolMatchBonus        = 0.3
-	// climateRegionBonus removed — suggestions now based on home features only
-	propertyTypeBonus     = 0.15
-	totalProfileFields    = 14
+	maxSuggestions     = 30
+	baseUniversalScore = 0.3
+	stringMatchBonus   = 0.25
+	boolMatchBonus     = 0.3
+	// climateRegionBonus is deliberately higher than stringMatchBonus —
+	// climate zone is coarse but high-signal (one bit for a whole region of
+	// templates like "Hurricane Prep" or "Winterize Sprinkler").
+	climateRegionBonus = 0.35
+	propertyTypeBonus  = 0.15
+	totalProfileFields = 15 // 14 home-profile fields + ZIP/region
 )
 
 // GetSuggestions returns task template suggestions scored against a residence's profile
@@ -87,7 +97,6 @@ func (s *SuggestionService) GetSuggestions(residenceID uint, userID uint) (*resp
 	if err := s.db.
 		Preload("Category").
 		Preload("Frequency").
-		Preload("Regions").
 		Where("is_active = ?", true).
 		Find(&templates).Error; err != nil {
 		return nil, apperrors.Internal(err)
@@ -308,6 +317,17 @@ func (s *SuggestionService) scoreTemplate(tmpl *models.TaskTemplate, residence *
 		}
 	}
 
+	// Climate region match. We resolve the residence's ZIP to a region ID on
+	// demand; a missing/invalid ZIP is treated the same as a nil home-profile
+	// field — no penalty, no exclusion.
+	if cond.ClimateRegionID != nil {
+		conditionCount++
+		if residenceRegionID := resolveResidenceRegionID(residence); residenceRegionID != 0 && residenceRegionID == *cond.ClimateRegionID {
+			score += climateRegionBonus
+			reasons = append(reasons, "climate_region")
+		}
+	}
+
 	// Cap at 1.0
 	if score > 1.0 {
 		score = 1.0
@@ -367,6 +387,30 @@ func CalculateProfileCompleteness(residence *models.Residence) float64 {
 	if residence.LandscapingType != nil {
 		filled++
 	}
+	// PostalCode is the 15th field — counts toward completeness when we can
+	// map it to a region. An invalid / unknown ZIP doesn't count.
+	if resolveResidenceRegionIDByZip(residence.PostalCode) != 0 {
+		filled++
+	}
 
 	return float64(filled) / float64(totalProfileFields)
 }
+
+// resolveResidenceRegionID returns the IECC climate zone ID for a residence
+// based on its PostalCode, or 0 if the ZIP can't be mapped. Helper lives here
+// (not in region_lookup.go) because it couples the Residence model to the
+// suggestion service's notion of region resolution.
+func resolveResidenceRegionID(residence *models.Residence) uint {
+	return resolveResidenceRegionIDByZip(residence.PostalCode)
+}
+
+func resolveResidenceRegionIDByZip(zip string) uint {
+	if zip == "" {
+		return 0
+	}
+	state := ZipToState(zip)
+	if state == "" {
+		return 0
+	}
+	return GetClimateRegionIDByState(state)
+}