chore: remove companion app (moved to calcom/companion)

[volnei]

What does this PR do?

Removes the companion/ directory and all associated CI configuration from this monorepo. The companion app (iOS, Android, browser extension) has been migrated to its own repository at calcom/companion with full commit history preserved.

Changes

• Deleted companion/ — all source code, configs, and assets
• Deleted companion CI workflows — companion-build.yml, companion-lint.yml, companion-typecheck.yml
• Deleted .github/ISSUE_TEMPLATE/companion.md
• Deleted .easignore — EAS Build ignore file (was solely for companion mobile builds)
• Updated .github/workflows/pr.yml — removed has-companion output, path filter, three companion CI jobs (build-companion, typecheck-companion, lint-companion), and their references in the required job's needs list and failure conditions
• Updated packages/lib/timeZones.ts — comment now points to calcom/companion repo instead of local companion/ path

Mandatory Tasks (DO NOT REMOVE)

• I have self-reviewed the code (A decent size PR without self-review might be rejected).
• I have updated the developer docs in /docs if this PR makes changes that would require a documentation change. N/A — deletion only, no docs impact.
• I confirm automated tests are in place that prove my fix is effective or that my feature works. N/A — deletion only; CI passing confirms no regressions.

How should this be tested?

1. Verify CI passes on this PR — the companion jobs should no longer appear in new workflow runs
2. Confirm no remaining references to companion/ in the repo outside of unrelated contexts (e.g., the Alby app-store description mentioning "companion" is unrelated)

Human Review Checklist

• pr.yml changes (most important) — Verify the required job's needs list and failure conditions are still structurally correct after removing the companion block. The conditional logic around has-agents-changes at the end of the failure check should still be properly connected.
• .easignore deletion — Confirm nothing else in the monorepo depends on this file
• No orphaned references — Verify no other CI workflows or configs still reference companion/

Note on expected CI behavior: The required check will fail on this PR because pull_request_target runs the workflow from main, which still defines the companion jobs. Since companion code is deleted in the PR, those jobs fail. This is a chicken-and-egg situation that resolves once merged. All code-specific checks (lint, type-check, unit tests) pass.

Link to Devin run: https://app.devin.ai/sessions/c426fbde722b4a668333a803306fd36e
Requested by: @volnei

[devin-ai-integration]

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[cubic-dev-ai]

No issues found across 301 files

Note: This PR contains a large number of files. cubic only reviews up to 75 files per PR, so some files may not have been reviewed.

[github-actions]

E2E results are ready!

• Workflow #104722.2 latest results

[keithwillcode]

Have to force merge because GitHub doesn’t use the updated GitHub actions here. It uses main instead so the checks fail