feat(ai): add MiniMax provider

[octo-patch]

Reason: Add a first-class MiniMax provider and expose the documented media input capabilities for its current models.

Changed:

• Added the MiniMax driver and registered it in the AI provider registry.
• Extended the admin provider catalog and credential forms for MiniMax base-URL setup.
• Added provider model lookup coverage and a MiniMax-specific driver test.
• Exposed video input metadata for the supported multimodal model while keeping the text-only model closed.
• Extended shared capability serialization and fail-closed capability resolution for video input.

Checks:

• bun test server/ai/drivers/minimax.test.ts src/__tests__/ai/modelCapabilities.test.ts
• bun test src/__tests__/ai/providersTab.test.tsx
• bun run lint
• bun run build

[octo-patch]

Updated this PR with MiniMax global/China endpoint presets for both supported wire protocols, required API-key handling, current M3/M2.7 metadata, and protocol-specific model discovery and streaming coverage. Focused tests, TypeScript checking, ESLint, and the production build pass; the two unrelated full-suite failures reproduce on the pre-change PR head.