Reduce dependency footprint

[adsharma]

Related: #25

Summary

• remove 14 direct npm dependencies from the app manifest and lockfile
• replace small dependency usage with local fetch, UUID, date formatting, logging, CORS, upload, drag/drop, color, and session persistence helpers
• keep existing API routes while changing import uploads to raw file bodies and session persistence to JSON

Direct dependencies remaining:

• 13 runtime dependencies
• 16 dev dependencies
• 29 total direct dependencies

Installed tree size is 1127 packages including transitive dependencies.

Validation

• npm run build
• NODE_ENV=production LBUG_IN_MEMORY=true npm run lint
• node --check src/server/Import.js
• node --check src/server/utils/SessionDatabase.js
• node --check src/server/utils/Logger.js

Notes

• Build passes with existing Sass deprecation and asset-size warnings.
• npm install still reports audit findings in the remaining dependency tree.