Reduce App Size & Build Time

Background: Native [platform] app. App download size is [size if known]
and/or build times are slowing me down. Dependencies: [rough list].

Use case: Shrink the binary the user downloads and/or speed up my builds.

Implementation details:
- App size: iOS—app thinning/bitcode-era considerations, asset catalog
  optimization, on-demand resources, auditing large dependencies and
  unused assets. Android—App Bundle + dynamic delivery, R8/ProGuard
  shrinking and resource shrinking, vector vs raster assets, splitting
  by density/abi.
- Find the biggest contributors first (size report / bundle analyzer)
  rather than guessing
- Build time: incremental build hygiene, modularization (Section 2.3) for
  parallel builds, trimming heavy dependencies, iOS build settings /
  Android Gradle config and caching
- Tradeoffs: don't sacrifice runtime perf or maintainability for marginal
  size wins

Deliverable: The measured top contributors to size (and build time), the
prioritized reductions per platform, the expected savings, and the
tradeoffs to accept or avoid.