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>

docs/openapi.yaml

@@ -523,39 +523,6 @@ paths:
                 items:
                   $ref: '#/components/schemas/TaskTemplateResponse'
 
-  /tasks/templates/by-region/:
-    get:
-      tags: [Static Data]
-      operationId: getTaskTemplatesByRegion
-      summary: Get task templates for a climate region by state or ZIP code
-      description: Returns templates matching the climate zone for a given US state abbreviation or ZIP code. At least one parameter is required. If both are provided, state takes priority.
-      parameters:
-        - name: state
-          in: query
-          required: false
-          schema:
-            type: string
-            example: MA
-          description: US state abbreviation (e.g., MA, FL, TX)
-        - name: zip
-          in: query
-          required: false
-          schema:
-            type: string
-            example: "02101"
-          description: US ZIP code (resolved to state on the server)
-      responses:
-        '200':
-          description: Regional templates for the climate zone
-          content:
-            application/json:
-              schema:
-                type: array
-                items:
-                  $ref: '#/components/schemas/TaskTemplateResponse'
-        '400':
-          $ref: '#/components/responses/BadRequest'
-
   /tasks/templates/{id}/:
     get:
       tags: [Static Data]
@@ -972,6 +939,34 @@ paths:
         '403':
           $ref: '#/components/responses/Forbidden'
 
+  /tasks/bulk/:
+    post:
+      tags: [Tasks]
+      operationId: bulkCreateTasks
+      summary: Create multiple tasks atomically
+      description: Inserts 1-50 tasks in a single database transaction. If any entry fails, the entire batch is rolled back. Used primarily by onboarding to create the user's initial task list in one request.
+      security:
+        - tokenAuth: []
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/BulkCreateTasksRequest'
+      responses:
+        '201':
+          description: All tasks created
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/BulkCreateTasksResponse'
+        '400':
+          $ref: '#/components/responses/ValidationError'
+        '401':
+          $ref: '#/components/responses/Unauthorized'
+        '403':
+          $ref: '#/components/responses/Forbidden'
+
   /tasks/by-residence/{residence_id}/:
     get:
       tags: [Tasks]
@@ -3690,6 +3685,38 @@ components:
           type: integer
           format: uint
           nullable: true
+        template_id:
+          type: integer
+          format: uint
+          nullable: true
+          description: TaskTemplate ID this task was spawned from (onboarding suggestion, browse-catalog pick). Omit for custom tasks.
+
+    BulkCreateTasksRequest:
+      type: object
+      required: [residence_id, tasks]
+      properties:
+        residence_id:
+          type: integer
+          format: uint
+          description: Residence that owns every task in the batch; overrides the per-entry residence_id.
+        tasks:
+          type: array
+          minItems: 1
+          maxItems: 50
+          items:
+            $ref: '#/components/schemas/CreateTaskRequest'
+
+    BulkCreateTasksResponse:
+      type: object
+      properties:
+        tasks:
+          type: array
+          items:
+            $ref: '#/components/schemas/TaskResponse'
+        summary:
+          $ref: '#/components/schemas/TotalSummary'
+        created_count:
+          type: integer
 
     UpdateTaskRequest:
       type: object
@@ -3827,6 +3854,11 @@ components:
           type: integer
           format: uint
           nullable: true
+        template_id:
+          type: integer
+          format: uint
+          nullable: true
+          description: TaskTemplate this task was spawned from; nil for custom user tasks.
         completion_count:
           type: integer
         kanban_column: