feat: Add file upload rules and size limits for different messaging channels

[iamsivin]

Summary table from your config + fallback logic:

Channel / Medium	Max size rule	Types used
Default	40 MB for all (no per-category overrides)	Default types: image *, audio *, video *, text csv, plain, rtf, xml, application json, pdf, xml, zip, 7z, rar, tar, doc/x, xls/x, ppt/x, odt (+ .3gpp ext)
WhatsApp *	image 5 MB, video 16 MB, audio 16 MB, document 100 MB	image jpeg, png; audio aac, amr, mp3, m4a, ogg; video 3gp, mp4; docs pdf, xls(x), doc(x), ppt(x)
Instagram *	image 16 MB, video 25 MB, audio 25 MB	image png, jpeg, gif; audio aac, m4a, wav, mp4; video mp4, ogg, avi, mov, webm
Facebook *	image 8 MB, video 25 MB, audio 25 MB, document 25 MB	image png, jpeg, gif; audio aac, m4a, wav, mp4; video mp4, ogg, avi, mov, webm; docs pdf, xls(x), doc(x), ppt(x)
LINE *	image 10 MB; video → falls back to 40 MB (no per-cat or channel max)	image png, jpeg; video mp4
Twilio – SMS	5 MB for all (channel max)	Default types (fallback): image *, audio *, video *, text csv, plain, rtf, xml, application list above
Twilio – WhatsApp	5 MB for all (channel max)	image png, jpeg; audio mpeg, opus, ogg, amr; video mp4; docs pdf

[github-actions]

size-limit report 📦

Path	Size
dist/utils.cjs.production.min.js	11.74 KB (+7.48% 🔺)
dist/utils.esm.js	11.29 KB (+9.02% 🔺)