config: build profiles with --profile on ios build and ios share

[Interlap01]

Summary

Build profiles in builder.json, modeled on eas.json:

"defaultProfile": "development",
"profiles": {
  "development": { "configuration": "Debug", "signing": false },
  "preview":     { "configuration": "Release", "signing": true, "env": { "API_URL": "https://staging.example.com" } },
  "production":  { "configuration": "Release", "signing": true, "scheme": "MyApp", "provider": "codemagic", "distribution": "app-store" }
}

• builder ios build --profile <name> and builder ios share --profile <name> select a profile; defaultProfile applies when no flag is given. Without either, dispatch inputs and Codemagic/Bitrise parameters are identical to before, pinned by tests.
• A profile overrides only the fields it sets (configuration, scheme, signing, provider, env, distribution); --unsigned and --provider still win. Unknown names error with the available list. Resolved settings are printed before dispatch.
• env reaches the runner as one JSON workflow input profile, keeping ios-build.yml under GitHub's ten-input cap with room for the upcoming build number. Resolve parameters writes it to $GITHUB_ENV with a random heredoc delimiter before any dependency or build step; tag-triggered runs read defaultProfile from builder.json. Codemagic/Bitrise receive BUILD_ENV and DISTRIBUTION, exported by runner.sh in prepare().
• Env names are validated and the runner's own parameters, the signing secrets, PATH/HOME/DEVELOPER_DIR, MOBAI_API_KEY and the GITHUB_/RUNNER_/CM_/BITRISE_/BUILDER_ namespaces are reserved. Env values are build configuration, not secrets: they appear in run inputs and logs, and the README says so.
• distribution is validated and passed through as steps.params.outputs.distribution / $DISTRIBUTION for the export step to consume in a follow-up.
• Dispatching with a profile against a committed workflow that predates this change now explains that builder init must be re-run and the workflow committed.

Test plan

• go build ./... && go vet ./... && go test ./..., gofmt -l . clean
• builder ios build without a profile on an existing project: same inputs and behavior as before
• builder ios build --profile preview after builder init: run log shows the env exported and Release
• builder ios build --profile nope lists the available profiles
• Tag-triggered build with defaultProfile set picks it up

[Interlap01]

Folded into #23, which carries these commits with the final profile design.