feat: support conversation isolation

[junwen-lee]

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 3.19787% with 2906 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
backend/api/model/conversation/message/message.go	0.00%	840 Missing ⚠️
...pi/model/conversation/conversation/conversation.go	0.00%	389 Missing ⚠️
backend/api/model/conversation/run/run.go	0.00%	326 Missing ⚠️
...pi/model/conversation/agentrun/agentrun_service.go	0.00%	199 Missing ⚠️
.../conversation/conversation/conversation_service.go	0.00%	199 Missing ⚠️
.../api/model/conversation/message/message_service.go	0.00%	199 Missing ⚠️
backend/infra/eventbus/impl/nats/consumer.go	0.00%	136 Missing ⚠️
backend/infra/eventbus/impl/nats/producer.go	0.00%	107 Missing ⚠️
backend/infra/embedding/impl/impl.go	0.00%	73 Missing ⚠️
...kend/application/conversation/openapi_agent_run.go	54.43%	67 Missing and 5 partials ⚠️
... and 38 more

Files with missing lines	Coverage Δ
backend/api/middleware/openapi_auth.go	0.00% <ø> (ø)
...onversation/internal/dal/model/conversation.gen.go	100.00% <ø> (ø)
...ersation/conversation/service/conversation_impl.go	58.33% <100.00%> (+0.88%)	⬆️
.../internal/nodes/conversation/createconversation.go	77.46% <100.00%> (ø)
backend/application/conversation/agent_run.go	0.00% <0.00%> (ø)
backend/application/conversation/message.go	2.02% <0.00%> (ø)
backend/bizpkg/llm/modelbuilder/builtin.go	0.00% <0.00%> (ø)
backend/bizpkg/llm/modelbuilder/deepseek.go	0.00% <0.00%> (ø)
backend/bizpkg/llm/modelbuilder/openai.go	0.00% <0.00%> (ø)
...kflow/internal/nodes/conversation/createmessage.go	45.74% <0.00%> (ø)
... and 42 more

... and 3 files with indirect coverage changes

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