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/repositories/task_template_repo_test.go

@@ -185,33 +185,6 @@ func TestTaskTemplateRepository_Count(t *testing.T) {
 	assert.Equal(t, int64(2), count) // Only active
 }
 
-func TestTaskTemplateRepository_GetByRegion(t *testing.T) {
-	t.Skip("requires PostgreSQL: SQLite cannot scan jsonb default into json.RawMessage")
-	db := testutil.SetupTestDB(t)
-	repo := NewTaskTemplateRepository(db)
-
-	// Create a climate region
-	region := &models.ClimateRegion{Name: "Hot-Humid", ZoneNumber: 1, IsActive: true}
-	require.NoError(t, db.Create(region).Error)
-
-	// Create template with region association
-	tmpl := &models.TaskTemplate{Title: "Regional Task", IsActive: true}
-	require.NoError(t, db.Create(tmpl).Error)
-
-	// Associate template with region via join table
-	err := db.Exec("INSERT INTO task_tasktemplate_regions (task_template_id, climate_region_id) VALUES (?, ?)", tmpl.ID, region.ID).Error
-	require.NoError(t, err)
-
-	// Create template without region
-	tmpl2 := &models.TaskTemplate{Title: "Non-Regional Task", IsActive: true}
-	require.NoError(t, db.Create(tmpl2).Error)
-
-	templates, err := repo.GetByRegion(region.ID)
-	require.NoError(t, err)
-	assert.Len(t, templates, 1)
-	assert.Equal(t, "Regional Task", templates[0].Title)
-}
-
 func TestTaskTemplateRepository_GetGroupedByCategory(t *testing.T) {
 	t.Skip("requires PostgreSQL: SQLite cannot scan jsonb default into json.RawMessage")
 	db := testutil.SetupTestDB(t)