feat: add connectors settings tab for DingTalk and XiaoShouYi integration

[xielixing]

Summary

Resolves #1562

This PR adds a Connectors settings tab that lets users connect to SaaS platforms like DingTalk (钉钉) and XiaoShouYi/Neocrm (销售易), enabling the AI agent to fetch and analyze data from these services.

Changes

• settingsConfig.ts: Add \connectors\ to \ConfigTab\ union type and register it in the \smartCapabilities\ category
• settingsContentRegistry.ts: Register lazy loader for the Connectors config component
• SettingsScene.tsx: Add \case 'connectors'\ to the content resolver switch
• settingsTabI18n.ts: Map the connectors tab to its i18n namespace
• ConnectorsConfig.tsx (new): Full settings panel with configured connector cards, add-connector dialog, provider catalog, and sync/test/delete actions
• ConnectorsAPI.ts (new): Type definitions for \ConnectorProvider, \ConnectorInstance, \ConnectorConfig, and a \connectorsAPI\ service with list/create/update/delete/test/sync methods
• i18n: New \settings/connectors\ namespace for en-US, zh-CN, zh-TW; updated \settings.json\ tab labels and descriptions for all three locales

Supported Providers

Provider	Capabilities
DingTalk (钉钉)	messages, contacts, approvals, calendar
XiaoShouYi (销售易/Neocrm)	leads, customers, opportunities, reports

Testing

• TypeScript/TSX validated via esbuild (exit code 0, no errors)
• All JSON locale files validated as valid JSON
• Component follows existing settings tab patterns (lazy load, i18n namespace, ConfigPageLayout)