fix: stop apify upgrade reporting success after a failed binary write

[l2ysho]

Note

TL;DR: On Unix bundle installs, apify upgrade printed "Successfully upgraded" and exited 0 even when downloading or writing the new binary failed. Now it skips the success message and exits 1.

Closes #1460

What changed

• handleUnixUpgrade returns Promise<boolean>. A failed download or write sets process.exitCode = 1 and returns false. The caller prints the success message only when the upgrade worked.
• A write failure now stops the upgrade right away instead of moving on to the next asset.
• New test/local/commands/upgrade.test.ts: success path, failed write (ETXTBSY), and failed download (404). Both failure tests fail on master and pass with this fix.

Notes for reviewers

• The ETXTBSY error in apify upgrade fails with ETXTBSY on Linux and still reports success #1460 is already fixed since v1.8.0 (feat: single apify-cli bundle + native Windows ARM64 (supersedes #1057) #1169): the new binary is written to a temp file and renamed into place. The reporter was upgrading from v1.7.1 or older, and that old upgrade code still runs during the upgrade, so this PR cannot help them. Workaround: curl -fsSL https://apify.com/install-cli.sh | bash.
• Follow-up: other error paths in upgrade still exit 0 (invalid version, missing assets, npm/pnpm/brew fallback failure). I left them out to keep this diff small.

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