Build mode footgun: `make web-apps-dev` produces a production build; add explicit dev/prod targets

[moodyjmz]

What we found

While fixing the mobile editor regression (web-apps, follows DocumentServer#258),
we hit a build-mode footgun that nearly invalidated the fix's testing. Three
overlapping problems:

1. The Makefile target names lie. In develop/setup/Makefile, web-apps and
   web-apps-dev produce identical output — both production. The only
   difference is web-apps runs npm ci and web-apps-dev skips it
   (CHECK_WEBAPPS_DEPS). So -dev means "skip dependency install," NOT
   "development mode." Anyone reading the name expects a dev build and gets prod.

2. The two webpack pipelines default NODE_ENV oppositely.

   • desktop web-apps/build/webpack.editor.factory.mjs → NODE_ENV || 'production'
   • mobile web-apps/vendor/framework7-react/build/webpack.config.js → NODE_ENV || 'development'
     So with NODE_ENV unset, desktop builds prod and mobile builds dev unless
     something forces it. A manual mobile build silently came out dev — esbuild's
     minimizer never runs in dev, so the production-only transforms (ES target
     downlevel, drop_console) don't execute.

3. The validation trap. Because a dev mobile build skips the minifier, a
   crash that only occurs in production (esbuild lowering i18next 25's class
   internals → TypeError: we is not a function) appears fixed in a dev build
   — the broken transform simply never ran. "It works in my rebuild" can mean
   "esbuild didn't run," not "the fix works." This cost real debugging time.

Fixes already landed in web-apps (companion PR)

• build-pipeline.js now sets NODE_ENV once in CHILD_ENV
  (process.env.NODE_ENV || 'production'), passed to every child — desktop and
  mobile now agree, defaulting to production, overridable with NODE_ENV=development.
• build-pipeline.js echoes the build mode in its banner (green production,
  red ⚠ DEV BUILD warning) so the mode is never silent again.
• Mobile watch decoupled from NODE_ENV (WATCH=1 opt-in) so a dev-mode build
  is a one-shot that exits, instead of hanging the pipeline in watch mode.

Proposed change here (DocumentServer Makefile)

Make the target suffix mean the mode, self-documenting, so the shell
environment can't silently flip it:

target	install	mode	use
web-apps	npm ci	production	canonical / first build
web-apps-prod	skip	production	fast re-test of the shipping build
web-apps-dev	skip	development	fast debuggable iteration

web-apps-dev:  NODE_ENV := development
web-apps-prod: NODE_ENV := production
web-apps-dev web-apps-prod:
	$(CHECK_WEBAPPS_DEPS)
	cd $(EO_DEV)/web-apps/translation && python3 merge_and_check.py && \
	cd $(EO_DEV)/web-apps/build && \
	BUILD_ROOT=$(EO_ROOT) PRODUCT_VERSION=$(PRODUCT_VERSION) THEME=euro-office \
	SKIP_MOBILE=$(SKIP_MOBILE) NODE_ENV=$(NODE_ENV) \
	node scripts/build-pipeline.js
	$(FLUSH_CACHE)

Heads-up / acceptance

• Behaviour change: make web-apps-dev flips from production → development.
  The dev-container docs (and web-apps CLAUDE.md) that point at make web-apps-dev must be updated: use web-apps-prod (or web-apps) to test the
  shipping build; web-apps-dev to debug.
• A dev build is unminified, keeps console, inlines CSS via style-loader, and
  does NOT exercise the production transforms — by design. Never sign off a fix on
  a dev build.
• web-apps-prod and web-apps produce the same bundle; web-apps-prod just
  skips npm ci for speed.