feat: add volcengine and byteplus provider presets

[Maaannnn]

Summary

• update the built-in volcengine preset to the standard Ark pay-as-you-go contract
• add built-in volcengine-coding-plan, byteplus, and byteplus-coding-plan presets
• migrate legacy local volcengine settings only when they still match the old bundled preset

Behavior Changes

• WorkAny now ships four built-in presets instead of only the legacy volcengine coding endpoint preset
• the built-in IDs follow the public contract directly: volcengine, volcengine-coding-plan, byteplus, byteplus-coding-plan
• standard and coding-plan variants use distinct base URLs and model catalogs, matching the requested provider matrix
• existing users with the old bundled volcengine preset are migrated forward without overwriting custom edits or API keys
• new default presets are appended for existing installs so the new providers appear in Settings automatically

Contract Choices

• scheme: 4-provider
• auth labels remain the existing provider-name-based UI labels in WorkAny; the preset metadata uses Volcengine / BytePlus naming consistently
• base URLs, model lists, API key links, and provider IDs were aligned to the requested Volcengine / BytePlus contract rather than the previous repo defaults
• no extra aliases were introduced because this repo stores provider IDs directly in local settings and does not expose a separate provider registry/menu contract here

Testing

• pnpm exec eslint src/shared/db/settings.ts
• pnpm build
• pnpm lint (still fails due unrelated pre-existing repo lint issues)

Risks / Follow-up

• no live API validation was run because no real Volcengine or BytePlus credentials were available in this branch
• this change updates bundled frontend provider presets only; if WorkAny later adds a stricter provider registry or onboarding flow for model providers, these four IDs should be kept in sync there as well