ci: dependabot timezone Europe/Prague -> Etc/UTC (estate standard)

[vreshch]

Summary

• Estate standard: dependabot schedule timezone is Etc/UTC everywhere, so the configured time is the literal UTC time.
• dependabot.yml was still on timezone: 'Europe/Prague', so time: '16:07' meant 14:07 UTC (CEST, UTC+2), not 16:07 UTC as intended by the prior cron-offset PR.
• All 3 ecosystems (npm, docker, github-actions) switched to timezone: 'Etc/UTC'; time: '16:07' unchanged, now literally 16:07 UTC.

Test plan

• YAML syntax valid
• npm run format:check / prettier clean
• CI green on this PR (pr-validation.yml)

[github-actions]

🎉 PR Validation ✅ PASSED

Commit: 6400ca3cc8453c8ae4c59ceea590ba436e45ec01
Branch: chore/dependabot-utc-timezone

Checks:

• ✅ Dependencies installed
• ✅ Linting passed
• ✅ Format check passed
• ✅ Build successful
• ✅ Docker build
• ✅ E2E tests

Visual Changes: 8 of 8 screenshots changed

📸 contacts desktop — 100% changed

📸 contacts mobile — 100% changed

📸 home desktop — 100% changed

📸 home mobile — 100% changed

📸 interests desktop — 100% changed

📸 interests mobile — 100% changed

📸 projects desktop — 100% changed

📸 projects mobile — 100% changed

Ready to merge! ✨

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⏰ Generated at: 2026-08-10T21:20:26.440Z