Add css & js webpack cache bust

[cstns]

Description

Add webpack cache bust capability for front end assets (css/js)

docs: https://webpack.js.org/guides/caching/

Related Issue(s)

closes #4098

Checklist

• I have read the contribution guidelines
• Suitable unit/system level tests have been added and they pass
• Documentation has been updated
  • Upgrade instructions
  • Configuration details
  • Concepts
• Changes flowforge.yml?
  • Issue/PR raised on FlowFuse/helm to update ConfigMap Template
  • Issue/PR raised on FlowFuse/CloudProject to update values for Staging/Production

Labels

• Includes a DB migration? -> add the area:migration label

[cstns]

All js/css assets should now be prepended with a hashed value based on their contents. When this hashed value changes it will force the browser to reload said assets and bust it's cache

[cstns]

webpack build output should reflect same hashed values as loaded in the browser:

[cstns]

staging built assets with new hashes:

#15 79.70 warn - You have enabled the JIT engine which is currently in preview.
#15 79.70 warn - Preview features are not covered by semver, may introduce breaking changes, and can change at any time.
#15 109.8 assets by info 5.45 MiB [immutable]
#15 109.8   assets by path ./assets/ 315 KiB 12 assets
#15 109.8   assets by path *.js 5.04 MiB 5 assets
#15 109.8   assets by path *.css 102 KiB
#15 109.8     asset main.95260d59a4e3571960d2.css 50.8 KiB [emitted] [immutable] (name: main)
#15 109.8     asset setup.95260d59a4e3571960d2.css 50.8 KiB [emitted] [immutable] (name: setup)
#15 109.8 assets by path ../ 26.7 KiB
#15 109.8   assets by path ../*.png 9.75 KiB
#15 109.8     asset ../ff-logo--wordmark-caps--dark.png 8.91 KiB [emitted] [from: frontend/public/ff-logo--wordmark-caps--dark.png] [copied]
#15 109.8     asset ../favicon-32x32.png 524 bytes [emitted] [from: frontend/public/favicon-32x32.png] [copied]
#15 109.8     asset ../favicon-16x16.png 341 bytes [emitted] [from: frontend/public/favicon-16x16.png] [copied]
#15 109.8   asset ../favicon.ico 15 KiB [emitted] [from: frontend/public/favicon.ico] [copied]
#15 109.8   asset ../../dist-setup/setup.html 983 bytes [emitted]
#15 109.8   asset ../index.html 954 bytes [emitted]
#15 109.8 asset favicon.ico 15 KiB [emitted]
#15 109.8 Entrypoint main [big] 2.46 MiB (315 KiB) = runtime.0fe3871cfbbab18136eb.js 3.45 KiB vendors.6a0287064d4a7dcf0589.js 1.03 MiB main.95260d59a4e3571960d2.css 50.8 KiB main.5cfa94b6855d4f4bd477.js 1.38 MiB 12 auxiliary assets
#15 109.8 Entrypoint setup [big] 2.43 MiB (315 KiB) = runtime.0fe3871cfbbab18136eb.js 3.45 KiB vendors.6a0287064d4a7dcf0589.js 1.03 MiB setup.95260d59a4e3571960d2.css 50.8 KiB setup.c07c15d94e17574ce4f4.js 1.35 MiB 12 auxiliary assets
#15 109.8 orphan modules 4.02 MiB (javascript) 8.24 KiB (runtime) [orphan] 2356 modules
#15 109.8 runtime modules 8.86 KiB 17 modules
#15 109.8 built modules 6.49 MiB (javascript) 315 KiB (asset) 50.8 KiB (css/mini-extract) [built] 743 modules
#15 109.8 
#15 109.8 WARNING in asset size limit: The following asset(s) exceed the recommended size limit (244 KiB).
#15 109.8 This can impact web performance.
#15 109.8 Assets: 
#15 109.8   main.5cfa94b6855d4f4bd477.js (1.38 MiB)
#15 109.8   setup.c07c15d94e17574ce4f4.js (1.35 MiB)
#15 109.8   async-vendors.cb8fa64356060c9dc31f.js (1.28 MiB)
#15 109.8   vendors.6a0287064d4a7dcf0589.js (1.03 MiB)
#15 109.8 
#15 109.8 WARNING in entrypoint size limit: The following entrypoint(s) combined asset size exceeds the recommended limit (244 KiB). This can impact web performance.
#15 109.8 Entrypoints:
#15 109.8   main (2.46 MiB)
#15 109.8       runtime.0fe3871cfbbab18136eb.js
#15 109.8       vendors.6a0287064d4a7dcf0589.js
#15 109.8       main.95260d59a4e3571960d2.css
#15 109.8       main.5cfa94b6855d4f4bd477.js
#15 109.8   setup (2.43 MiB)
#15 109.8       runtime.0fe3871cfbbab18136eb.js
#15 109.8       vendors.6a0287064d4a7dcf0589.js
#15 109.8       setup.95260d59a4e3571960d2.css
#15 109.8       setup.c07c15d94e17574ce4f4.js
#15 109.8 

[knolleary]

Tested locally - looks good