Fix state persistence sharing and harden CI smoke coverage

[joecorall]

• Improve persistent state sharing with dirty-state saves, reconciliation, atomic writes, and jittered save timing.
• Move core Traefik label behavior into faster Go tests, leaving CI integration as a simpler smoke test across Traefik versions.
• Harden state persistence security by redacting secretKey, using private state/lock file modes, and using crypto/rand for jitter

[codecov-commenter]

Codecov Report

❌ Patch coverage is 73.85057% with 91 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
internal/state/state.go	64.61%	39 Missing and 30 partials ⚠️
main.go	85.50%	16 Missing and 4 partials ⚠️
internal/state/lock.go	86.66%	1 Missing and 1 partial ⚠️

Files with missing lines	Coverage Δ
internal/state/lock.go	85.00% <86.66%> (+4.60%)	⬆️
main.go	84.63% <85.50%> (+5.15%)	⬆️
internal/state/state.go	68.96% <64.61%> (-8.68%)	⬇️

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[github-actions]

Running State Persistence Stress Tests

Testing Small, Medium, Large, and XLarge scales...

Stress Test Summary

Scale	Entries	JSON Size	Time	Threshold	Status
Small	16 rate / 256 verified	16.08 KB	2ms	<500ms	✅
Medium	256 rate / 65K verified	3.90 MB	106ms	<1s	✅
Large	1K rate / 262K verified	15.59 MB	545ms	<3s	✅
XLarge	4K rate / 1M verified	62.74 MB	2536ms	<10s	✅

ℹ️ Performance metrics reported (thresholds informational only in CI)