v1.44.8: an uploaded plan never reached the config

Found on the owner's install: the image lands in /config/houseplan/plans, the
space keeps plan_url=null, the plan never shows and re-saving does not help.

_saveSpaceDialog held a reference to the space object across the await that
uploads the file. _reloadConfigOnly() — which runs on every
houseplan_config_updated event — REPLACES _serverCfg, so that reference became
an orphan: plan_url, aspect, title and every display setting were written into a
detached object while the save shipped the untouched config. In 'create' mode
the whole new space was lost the same way.

- upload first, then touch the config; no reference is held across an await.
- _saveConfigNow() sets _cfgWriting like the debounced writer, so a revision
  arriving mid-save defers its reload instead of replacing the config (audit L2
  extended to this path).
- demo/smoke_plan_upload_race.mjs: on v1.44.7 the sent config still carries the
  OLD plan_url and the created space is missing; passes here. The demo's
  config/get now returns a fresh object, as a real server does — returning the
  same reference is what hid this class of bug from the smoke layer.
- DEVELOPMENT.md: the deploy target is custom_components/houseplan/frontend/,
  and deploy verification must go over HTTP. A copy placed next to __init__.py
  is served by nobody — that cost two deployments today.
- docs: CHANGELOG.md + CHANGELOG.ru.md + TESTING.md + STATUS.md.

docs/TESTING.md

@@ -234,6 +234,11 @@ Run the *core flows* (marked ★ below) in each environment at least once per mi
       are only reachable through /api/houseplan/content/… with a session; the
       old /houseplan_files/plans|files paths return 404 after a restart; old
       stored URLs keep working (rewritten on read) [auto+manual]
+- [ ] Plan upload survives a concurrent config revision (v1.44.8): with a second
+      tab open on the same plan, attach a background image in space settings —
+      the plan shows immediately, `plan_url` is in `.storage/houseplan.config`,
+      and the same holds when the space is being CREATED, not edited
+      [auto: smoke_plan_upload_race]
 - [ ] Signed plan background (v1.44.7): a space whose plan lives on the content
       endpoint renders its background image with an `authSig` query — the plan is
       visible after a plain page load, and Home Assistant logs NO failed-login