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/handlers/handler_coverage_test.go

@@ -1664,27 +1664,10 @@ func TestTaskTemplateHandler_GetTemplatesByCategory(t *testing.T) {
 	})
 }
 
-func TestTaskTemplateHandler_GetTemplatesByRegion(t *testing.T) {
-	handler, e, db := setupTaskTemplateHandler(t)
-	testutil.SeedLookupData(t, db)
-
-	e.GET("/api/tasks/templates/by-region/", handler.GetTemplatesByRegion)
-
-	t.Run("missing both state and zip returns 400", func(t *testing.T) {
-		w := testutil.MakeRequest(e, "GET", "/api/tasks/templates/by-region/", nil, "")
-		testutil.AssertStatusCode(t, w, http.StatusBadRequest)
-	})
-
-	t.Run("with state param returns 200", func(t *testing.T) {
-		w := testutil.MakeRequest(e, "GET", "/api/tasks/templates/by-region/?state=TX", nil, "")
-		testutil.AssertStatusCode(t, w, http.StatusOK)
-	})
-
-	t.Run("with zip param returns 200", func(t *testing.T) {
-		w := testutil.MakeRequest(e, "GET", "/api/tasks/templates/by-region/?zip=78701", nil, "")
-		testutil.AssertStatusCode(t, w, http.StatusOK)
-	})
-}
+// NOTE: TestTaskTemplateHandler_GetTemplatesByRegion was removed. The
+// /api/tasks/templates/by-region/ endpoint was deleted; climate-zone
+// affinity is now a JSON condition on each template and is scored by the
+// main /api/tasks/suggestions/ endpoint (see SuggestionService tests).
 
 func TestTaskTemplateHandler_GetTemplate(t *testing.T) {
 	handler, e, db := setupTaskTemplateHandler(t)