chore: disable on-demand asset compilation and normalize Gemfile.lock platforms (#7040)

[augustocbx]

What github issue is this PR for, if any?

Addresses the two High priority (real impact) items of #7040. The remaining medium/low-priority checklist items (npm audit, Ruby patch bump, deprecated packages, install-script allowlist) are left as follow-ups, so this does not close the issue.

What changed, and why?

Two deploy-log hardening items from #7040:

1. Disabled on-demand asset compilation in production. The casa-qa build log warns that config.assets.compile = true in production. Assets are already precompiled at build time (rake assets:precompile runs during the build), so on-demand compilation only adds per-request latency and load — and it silently masks a missing precompiled asset instead of failing fast. Set config.assets.compile = false in config/environments/production.rb, which is the standard Rails production default for a precompiled app.

2. Normalized Gemfile.lock platforms. The build warns that the platform-specific ffi-1.17.2 gem is installed while the lockfile only carried OS-version-pinned platforms. Ran bundle lock --normalize-platforms, which collapses the version-pinned entries (arm64-darwin-21/22, x86_64-darwin-21/23) to their generic forms (arm64-darwin, x86_64-darwin). The ruby and x86_64-linux (Heroku) platforms are retained and the platform-specific gem specs are unchanged. bundle check passes after the change.

How is this tested? (please write rspec and jest tests!) 💖💪

These are production config / lockfile changes with no application-behavior surface, so there is no meaningful RSpec/Jest test to add (the test environment does not load config/environments/production.rb, and there is no existing convention in this repo for asserting environment config). Verification instead:

• ruby -c config/environments/production.rb → Syntax OK.
• bundle exec standardrb config/environments/production.rb → exit 0, no offenses.
• bundle lock --normalize-platforms produced a minimal diff touching only the PLATFORMS block (2 insertions, 4 deletions); bundle check → "The Gemfile's dependencies are satisfied".
• Assets continue to be resolved from the precompiled manifest; the build already runs rake assets:precompile successfully, so compile = false has all referenced assets available.

Screenshots please :)

Not applicable — no user-facing UI change (production configuration and dependency lockfile only).