refactor(api): Clean DB session - non pure-mechanic part

[cqjjjzr]

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Summary

Continuation of #38227, the non-mechanic possibly behavior changing parts.

Checklist

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran make lint && make type-check (backend) and cd web && pnpm exec vp staged (frontend) to appease the lint gods

[github-actions]

Pyrefly Diff

base → PR

--- /tmp/pyrefly_base.txt	2026-07-09 07:52:58.553052078 +0000
+++ /tmp/pyrefly_pr.txt	2026-07-09 07:52:49.028009143 +0000
@@ -8066,12 +8066,8 @@
    --> tests/unit_tests/services/test_summary_index_service.py:118:82
 ERROR Key `a` is not defined in TypedDict `SummaryIndexSettingDict` [bad-typed-dict-key]
    --> tests/unit_tests/services/test_summary_index_service.py:118:83
-ERROR Object of class `NoneType` has no attribute `status` [missing-attribute]
-    --> tests/unit_tests/services/test_summary_index_service.py:1024:12
-ERROR Object of class `NoneType` has no attribute `error` [missing-attribute]
-    --> tests/unit_tests/services/test_summary_index_service.py:1025:39
 ERROR Object of class `NoneType` has no attribute `endswith` [missing-attribute]
-    --> tests/unit_tests/services/test_summary_index_service.py:1086:12
+    --> tests/unit_tests/services/test_summary_index_service.py:1181:12
 ERROR Cannot set item in `dict[str, int]` [unsupported-operation]
    --> tests/unit_tests/services/test_variable_truncator.py:142:31
 ERROR Argument `dict[str, dict[Unknown, Unknown]]` is not assignable to parameter `node_config` with type `NodeConfigDict` in function `services.trigger.webhook_service.WebhookService.generate_webhook_response` [bad-argument-type]

[github-actions]

Pyrefly Type Coverage

Metric	Base	PR	Delta
Type coverage	52.64%	52.65%	+0.00%
Strict coverage	52.16%	52.17%	+0.00%
Typed symbols	32,587	32,593	+6
Untyped symbols	29,585	29,585	0
Modules	2982	2982	0