Lazy-load Client List stylesheet

[elkimek]

What changed

• replace the eager Client List stylesheet link with an ordered lazy-load anchor
• load css/client-list.css on the first Client List open, single-flight concurrent opens, and retry safely after failures
• keep the stylesheet in the service-worker app shell for offline first use
• add real shell-entry, concurrency, retry, cold-load, and Firefox offline coverage
• ratchet the committed cold-load budget and bump the app version

Why

Client List is not visible during a returning-user startup, but its 17.5 KB stylesheet was fetched on every cold load. Deferring it to the feature boundary removes startup work without making the module itself lazy or changing its shell/profile/location integrations.

Impact

Identical before/after cold mobile runs reduced startup from 441 to 440 requests, 1,857,409 to 1,854,314 compressed bytes, and 5,650,563 to 5,635,229 decoded bytes. The modal now waits for its CSS before opening; a failed load is contained and the next open retries.

Validation

• COVERAGE=1 PORT=8271 ./run-tests.sh
• 487 Vitest tests passed
• 399 Chromium tests passed
• 472 responsive checks passed
• Firefox offline smoke: 3 passed
• audit: 338 passed
• combined function coverage: 67.11% (ratchet: 67.10%)
• cold-load budget reproduced exactly: 440 requests / 1,854,314 compressed / 5,635,229 decoded