[ISSUE #15416] Support Nacos-managed skill subscriptions

[saynoword]

Please do not create a Pull Request without creating an issue first.

What is the purpose of the change

Add Nacos-managed skill subscriptions so users can maintain per-user, per-namespace skill subscription lists from Nacos and let CLI registry mode read the current user's subscription list. This stores subscriptions in Config without adding a new table, exposes admin/console management APIs plus a client read API, and wires the old console and next console subscription workflows. Closes #15416.

Brief changelog

• Add skill subscription API models, Config-backed storage, admin subscription service, and current-user client subscription read service.
• Add admin APIs for listing, subscribing, and unsubscribing skills, plus a client API that only reads the current request user's subscriptions.
• Wire console maintainer/inner/noop handlers and old console skill management subscription UI.
• Add next console subscription state, single and batch subscription actions, "My subscriptions" filtering, skill detail subscription controls, and synced static assets.
• Update skill specs, API surface docs, OpenAPI scenario coverage, and targeted unit/API tests.

Verifying this change

• mvn -pl api,ai,maintainer-client,test/openapi-test -DskipTests spotless:apply
• mvn -pl api,ai,maintainer-client,test/openapi-test -DskipTests spotless:check
• mvn -pl ai -am -Dtest=SkillAdminControllerTest,SkillSubscriptionServiceImplTest,ConfigSkillSubscriptionStorageTest -Dsurefire.failIfNoSpecifiedTests=false test
• mvn -pl console -am -Dtest=ConsoleSkillControllerTest,SkillProxyTest,SkillInnerHandlerTest,SkillRemoteHandlerTest -Dsurefire.failIfNoSpecifiedTests=false test
• mvn -pl ai -am -Dtest=SkillClientControllerTest,ConfigSkillSubscriptionStorageTest,SkillSubscriptionServiceImplTest,SkillClientSubscriptionServiceImplTest -Dsurefire.failIfNoSpecifiedTests=false test
• mvn -pl test/openapi-test -DskipTests test-compile
• npx eslint src/pages/skillManagement/index.tsx

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[github-actions]

Thanks for your this PR. 🙏
Please check again for your PR changes whether contains any usage/api/configuration change such as Add new API , Add new configuration, Change default value of configuration.
If so, please add or update documents(markdown type) in docs/next/ for repository nacos-group/nacos-group.github.io

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感谢您提交的PR。 🙏
请再次查看您的PR内容，确认是否包含任何使用方式/API/配置参数的变更，如：新增API、新增配置参数、修改默认配置等操作。
如果是，请确保在提交之前，在仓库nacos-group/nacos-group.github.io中的docs/next/目录下添加或更新文档（markdown格式）。