refactor: migrate native module from Expo Modules API to React Native Turbo Modules

[V3RON]

Why this matters

This branch finishes the move away from the old monolithic voltra package and lands the package layout that matches how the library is actually structured now.

Instead of shipping one mixed package with Expo Modules-era assumptions, Voltra is now split into explicit platform and responsibility-focused workspaces:

• @use-voltra/ios-client and @use-voltra/android-client for React Native client APIs and native bindings
• @use-voltra/ios and @use-voltra/android for platform JSX/runtime packages
• @use-voltra/ios-server, @use-voltra/android-server, and @use-voltra/server for server rendering flows
• @use-voltra/generator as the private source of truth for generated component metadata
• @use-voltra/expo-plugin as shared plugin utilities used by the client packages

The branch also removes the old packages/voltra workspace entirely, updates docs/examples to the new install/import paths, and adds regression coverage around renderer/server/generator behavior so the split is safer to maintain.

Closes #148

What changed

Package and workspace restructuring

• migrated the native module work into @use-voltra/ios-client and @use-voltra/android-client
• kept platform JSX/runtime code in @use-voltra/ios and @use-voltra/android
• introduced dedicated server packages: @use-voltra/server, @use-voltra/ios-server, @use-voltra/android-server
• extracted generation logic and schemas into the private @use-voltra/generator workspace
• removed the legacy packages/voltra package instead of keeping it as a compatibility layer

Native and plugin integration cleanup

• completed the Turbo Module / Fabric-oriented native client setup in the split client packages
• added codegenConfig to iOS and Android client packages
• moved Expo config plugin entry points into the client packages while keeping shared plugin helpers in @use-voltra/expo-plugin
• preserved plugin build output and restored monorepo Babel/Jest/example app setup needed by the new workspace layout

Shared rendering and server changes

• updated renderer/server packages to use the generated component id registries from the new generator workspace
• fixed prerender package imports after the workspace split
• aligned example app imports and server code with the new package boundaries

Tests and CI

• added regression coverage for:
• @use-voltra/core renderer
• @use-voltra/ios renderer
• @use-voltra/android renderer
• @use-voltra/server
• @use-voltra/ios-server
• @use-voltra/android-server
• @use-voltra/generator
• switched JS test execution to turbo run test
• added/updated expo-plugin validation tests in split client packages
• removed workspace smoke checks in favor of the more targeted regression suites above

Docs and examples

• updated README, CONTRIBUTING, website docs, and agent skill references to the new package names and setup flow
• updated the example app configuration and imports to use @use-voltra/ios-client / @use-voltra/android-client
• refreshed installation/setup guidance around platform-specific client packages and plugin usage

Test plan

• JS test suites run via Turbo (npm run test:js)
• Regression tests added for core/platform/server/generator packages
• Expo plugin validation tests added for split client packages
• iOS example app manual verification: Live Activities, widgets, VoltraView, events
• Android example app manual verification: widgets, ongoing notifications, VoltraView, events
• Bare React Native manual verification: install split client packages and confirm no legacy monolithic package assumptions remain