Optimize visual assets and loading

[teemoZipsa]

What changed

• replaced oversized generated raster images with project-specific SVG illustrations
• converted regional, weather, facility, and tool imagery to WebP
• added matching favicon, PWA, maskable, and Apple touch icons
• added explanatory diagrams to water pressure, hose deployment, SCBA, and Hazmat tools
• prioritized the dashboard region image for LCP discovery
• removed legacy image entries from the service worker data cache without deleting offline operational data

Why

The previous image set was roughly 65 MB, included several 9 MB generated images, and reused unrelated imagery for operational tools. Existing users could also retain those removed images in the version-independent offline cache.

Impact

• total source image footprint is reduced to about 2.73 MB
• quick tools and calculators now use semantically accurate visual guidance
• the primary dashboard image is discovered earlier by the browser
• legacy cached PNG assets are removed during service worker activation

Validation

• npm run lint
• frontend and Worker TypeScript checks
• npm run test:unit — 210 passed
• npm run test:worker — 33 passed
• npm run build
• npm run test:e2e — 5 UI and 2 offline tests passed