docs: migrating from dfx guide

[marc0olo]

Summary

• Synced migration guide from dfinity/icp-cli covering command mapping, config conversion, identity migration, and step-by-step checklist
• Adapted heading casing, removed emoji, replaced "Getting Help" with "Next steps" linking to quickstart and icp-cli docs
• Content is largely preserved from upstream with minimal adaptations for this docs site

Sync recommendation

sync from dfinity/icp-cli docs/migration/from-dfx.md

[marc0olo]

Review

Must-fix

1. AGENTS.md policy reversal — The PR removes the requirement that icskills be listed in <!-- Upstream: --> comments, but commit 1dcff44 on main explicitly strengthened that requirement. This change must be dropped during rebase.

2. Needs rebase on main — Branch is behind by 3 commits. The diff currently includes spurious changes from PRs docs: access management guide #29 and docs: asset canister guide #30 (asset-canister and access-management pages). Rebase will clean this up.

Suggestions

1. Recipe versions behind icp-cli skill — Page uses @dfinity/rust@v3.0.0 and @dfinity/motoko@v4.0.0, but the skill recommends v3.2.0 and v4.1.0. Since this is a synced page, fix should go upstream in dfinity/icp-cli.

2. Missing migration topics from the icp-cli skill — The skill's dfx-migration.md covers port changes (4943→8000), .env file removal, @dfinity/* → @icp-sdk/* package migration, and a verification checklist. Worth proposing upstream.

3. External link https://cli.internetcomputer.org/ — couldn't be verified as live. May want to link to the GitHub repo as fallback.

Verified

• Content is faithful to upstream .sources/icp-cli/docs/migration/from-dfx.md
• All CLI commands verified against .sources/icp-cli/docs/reference/cli.md
• Internal link to quickstart resolves
• <!-- Upstream: --> comment present and correct
• PR description has ## Sync recommendation
• Frontmatter complete, build passes, plain .md