refactor(api): extract workspace list into layered application service

[41tair]

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Summary

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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 Type Coverage

Metric	Base	PR	Delta
Type coverage	56.86%	56.88%	+0.02%
Strict coverage	56.38%	56.41%	+0.03%
Typed symbols	37,167	37,201	+34
Untyped symbols	28,442	28,439	-3
Modules	3092	3100	+8

[github-actions]

Pyrefly Diff

base → PR

--- /tmp/pyrefly_base.txt	2026-07-31 05:42:48.557399088 +0000
+++ /tmp/pyrefly_pr.txt	2026-07-31 05:42:38.676300375 +0000
@@ -2115,11 +2115,11 @@
 ERROR `SimpleNamespace` is not assignable to attribute `_current_tenant` with type `Tenant | None` [bad-assignment]
    --> tests/unit_tests/controllers/console/test_workspace_members.py:188:43
 ERROR Argument `Literal['app']` is not assignable to parameter `resource_type` with type `RBACResourceScope` in function `controllers.common.wraps._extract_resource_id` [bad-argument-type]
-   --> tests/unit_tests/controllers/console/test_wraps.py:310:41
+   --> tests/unit_tests/controllers/console/test_wraps.py:352:41
 ERROR Argument `Literal['app']` is not assignable to parameter `resource_type` with type `RBACResourceScope` in function `controllers.common.wraps._extract_resource_id` [bad-argument-type]
-   --> tests/unit_tests/controllers/console/test_wraps.py:318:41
+   --> tests/unit_tests/controllers/console/test_wraps.py:360:41
 ERROR Argument `list[FromClause]` is not assignable to parameter `tables` with type `Sequence[Table] | None` in function `sqlalchemy.sql.schema.MetaData.create_all` [bad-argument-type]
-  --> tests/unit_tests/controllers/console/workspace/test_workspace.py:45:54
+  --> tests/unit_tests/controllers/console/workspace/test_workspace.py:52:54
 ERROR `SimpleNamespace` is not assignable to attribute `db` with type `SQLAlchemy` [bad-assignment]
   --> tests/unit_tests/controllers/files/test_image_preview.py:18:17
 ERROR `SimpleNamespace` is not assignable to attribute `request` with type `Request` [bad-assignment]