fix(web): raise boot gzip ceiling for v1.3.160 staging builds

[tyler-dane]

What and why

Release v1.3.160 failed on staging-cloud at the boot-size gate while building the environment-specific web image (workflow run 38605496150, job 115996503289, commit 6369772 / #4462). staging-selfhosted on the same commit succeeded.

Measured boot-set gzip on the failing build: 520,057 B (85 chunks). Previous ceiling was 519,906 B (totalGzipBytes 518,882 + totalGzipSlackBytes 1,024), 151 B over.

Raise totalGzipBytes to 519,500 so the effective ceiling is 520,524 B (~467 B headroom above the measured gzip), consistent with prior ceiling bumps (#4317, #4196, #4144, #4134, #4117).

Verify

Selected packages: web
Checks run: test:web, type-check, lint, knip, test:a11y, test:e2e
Checks skipped: (none)

✓ All checks passed
VERDICT: PASS

Additional boot-size evidence:

• cd apps/calendar-web && COMPASS_CONFIG_FILE=$PWD/../../.github/perf/compass.perf.yaml bun run build.ts → gzip 519,742 B
• .github/perf/run-boot-size-check.sh (deploy-aligned) → gzip 519,809 B