GitHub actions workflow

[gloskull]

Motivation
Reduce CI runtime and wasted runner time by parallelizing frontend checks and sharding long-running tests.
Harden workflows with concurrency cancellation, least-privilege permissions and job timeouts to improve CI reliability.
Fix existing lint/test regressions that prevented a green CI run.
Description
Split .github/workflows/frontend-ci.yml into independent lint, typecheck, unit-tests, build, and sharded e2e-tests jobs, added a ci-complete aggregation job, plus concurrency, job timeout-minutes, and permissions settings.
Touched .github/workflows/visual-regression.yml to add concurrency, explicit permissions, a timeout-minutes, and limited Playwright workers with --workers=50%.
Fixed heatmap wiring in src/components/map/AssetHeatmapLayer.tsx by calling the onTileUpdate callback and adding it to the effect dependency list, and removed an unused import.
Normalized tile key formatting in src/components/map/boundaryManager.ts from layer::x,y to layer:x:y.
Fixed sha256Hex in src/services/keyCache.ts by normalizing input bytes (new Uint8Array(bytes)) before calling crypto.subtle.digest to avoid runtime errors in tests.
Testing
Parsed workflows with Ruby/YAML to validate outputs via ruby -e "require 'yaml'; Dir['.github/workflows/*.yml'].each { |f| YAML.load_file(f); puts "parsed #{f}" }" which succeeded.
Ran static checks: npm run lint and npx tsc --noEmit, both succeeded after fixes.
Ran unit/component and integration tests with npm run test, all tests passed (547 tests passed).
Attempted npm run build but the Next.js production build failed in this environment due to inability to fetch Google Fonts from fonts.googleapis.com, so build steps should be re-run in CI or an environment with network access to Google Fonts.
Closes #128

[elizabetheonoja-art]

resolve conflicts @gloskull

[JerryIdoko]

resolve conflicts @gloskull

[elizabetheonoja-art]

resolve conflicts @gloskull

[elizabetheonoja-art]

resolve conflicts @gloskull