feat: support multiple canvas_types for agent templates and remove duplicate files (#14030)

### What problem does this PR solve?

Closes #13907

The template catalog had duplicate files (e.g. `*_r.json`) only to place
the same template into multiple sidebar groups.
This increases maintenance cost and makes template updates error-prone.

This PR adds first-class support for multiple template categories in a
single file via `canvas_types`, then removes duplicate template files.

What changed:
- Added `canvas_types` to `CanvasTemplate` model and DB migration.
- Added normalization logic when loading templates:
  - accepts legacy `canvas_type`
  - accepts new `canvas_types`
  - merges/deduplicates values
- preserves backward compatibility by keeping `canvas_type` as first
normalized value.
- Updated template import flow to load only `.json` files and in stable
sorted order.
- Updated frontend template filtering to match on `canvas_types` first,
with fallback to legacy `canvas_type`.
- Consolidated duplicated template pairs into single files and removed:
  - `deep_search_r.json`
  - `reflective_academic_paper_generator_r.json`
  - `seo_article_writer_r.json`
- Added regression/edge-case tests for category normalization and route
serialization expectations.

### Type of change

- [ ] Bug Fix (non-breaking change which fixes an issue)
- [x] New Feature (non-breaking change which adds functionality)
- [ ] Documentation Update
- [ ] Refactoring
- [ ] Performance Improvement
- [ ] Other (please describe):

api/db/init_data.py

@@ -35,6 +35,7 @@ from api.db.services.llm_service import LLMService, LLMBundle, get_init_tenant_l
 from api.db.services.user_service import TenantService, UserTenantService
 from api.db.services.system_settings_service import SystemSettingsService
 from api.db.services.dialog_service import DialogService
+from api.db.template_utils import normalize_canvas_template_categories
 from api.db.joint_services.memory_message_service import init_message_id_sequence, init_memory_size_cache, fix_missing_tokenized_memory
 from api.db.joint_services.tenant_model_service import get_tenant_default_model_by_type
 from common.constants import LLMType
@@ -166,16 +167,21 @@ def add_graph_templates():
         logging.warning("Missing agent templates!")
         return
 
-    for fnm in os.listdir(dir):
+    for fnm in sorted(os.listdir(dir)):
+        if not fnm.endswith(".json"):
+            logging.debug("Skipping non-json template file in %s: %s", dir, fnm)
+            continue
+        template_path = os.path.join(dir, fnm)
         try:
-            with open(os.path.join(dir, fnm), "r", encoding="utf-8") as f:
-                cnvs = json.load(f)
+            with open(template_path, "r", encoding="utf-8") as f:
+                cnvs = normalize_canvas_template_categories(json.load(f))
+            logging.info("Loaded and normalized template file: %s", template_path)
             try:
                 CanvasTemplateService.save(**cnvs)
             except Exception:
                 CanvasTemplateService.update_by_id(cnvs["id"], cnvs)
         except Exception as e:
-            logging.exception(f"Add agent templates error: {e}")
+            logging.exception("Add agent templates error for %s: %s", template_path, e)
 
 
 def init_web_data():