refactor(dx): consolidate Rspack bundler and dependencies

[Iru89]

Summary

• Move the Rspack baseline config and bundler dependencies into @botonic/dx, and remove the @botonic/dx-bundler-rspack workspace.
• Move DX and ESLint configuration dependencies out of the monorepo root into their owning packages; keep shared root tools needed by scripts and migrated packages.
• Update DX documentation, the CLI diagnostic, the package verifier, and the root lockfile.

Validation

• npm ci and npm run build
• Tests for core, react, the three plugins, and CLI (all passed; CLI was rerun with npm network access)
• npm run lint:check -w @botonic/cli
• node scripts/build/verify-packages.mjs (isolated consumer and Rspack bundle)
• Independent docs install, Docusaurus build, and npm run lint_ci

Note

The examples' lockfiles still pin previously published DX versions, which depend on the old bundler package. Their manifests remain unchanged, as agreed; the isolated consumer verifies the new DX package.

[chatgpt-codex-connector]

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