docs: everything caught up with v1.51.1

A sweep of every document against the shipped behaviour:

- README en+ru: the space dialog no longer claims a background is mandatory
  (draw-by-hand and the saved-plans picker exist; the canvas is square);
  'Show all devices' sections rewritten for the hide-flag world — the
  checkbox, 'Show hidden' ghosts, LQI-yes/light-no; troubleshooting updated.
- ARCHITECTURE: the config schema block still described v1.3 —
  aspect/device_overrides/virtual_devices/1000x1000-per-aspect/legacy-bundle
  fallback, all long gone. Rewritten to the current shape (square canvas,
  markers with hidden, filter_seeded, quotas, signed urls). The WS table
  dropped houseplan/file/set (removed in v1.10.0) and gained
  geometry/repair, layout/delete, files/migrate, files/cleanup,
  content/sign, the plans/list cap.
- UX-MODES: the Devices-tab tool list names the checkbox and the local
  'Show hidden' instead of the retired shared show-all.
- ROADMAP: repair-issues, system_health, floors import, data icon rules,
  click actions, theming and JSON i18n were done releases ago — checked off
  with their versions; the HACS pointer is #9004 (bot closed #8995).
- STATUS: SSH port is 22222 and the HA config root is
  /mnt/data/supervisor/homeassistant (/config does not exist there); the
  key lives in houseplan/.secrets; the PAT note reflects the fine-grained
  token; the feature surface gained the v1.42-v1.51 era.
- DEVELOPMENT: deploy instructions with the real port, path and cache
  busting.
- The owner's product description (user folder) refreshed the same way:
  square canvas, hide flags, the yellow principle.

README.md

@@ -161,7 +161,7 @@ for each floor (names prefilled, a plan image is asked for one by one; any floor
 
 ![Empty plan — prompt to add a space](docs/images/02-onboarding-empty.png)
 
-In the dialog, set a **name** (for example, "1st floor") and **upload a background** — a floor-plan image in SVG, PNG or JPG format. Both fields are required: without a plan the "Save" button stays disabled.
+In the dialog, set a **name** (for example, "1st floor") and pick the background: **upload** a floor-plan image (SVG, PNG, JPG, WebP), **choose one already uploaded** to the server earlier, or select **"no background, I'll draw the rooms"** for a hand-drawn space. The canvas is always square; an image keeps its own proportions and is centred inside it.
 
 ![Space creation dialog](docs/images/03-space-dialog.png)
 
@@ -204,7 +204,7 @@ walls** (it slides around corners too), and a **double click opens its propertie
 
 As soon as you save a room bound to an area, **the devices of that area are automatically laid out inside the outline**. These are the same devices shown on the **Settings → Devices → (filtered by the room)** page — only the meaningful ones, without service records, bridges and duplicates.
 
-By default only meaningful devices make it onto the plan — service records, bridges and duplicates are filtered out. If you need to see **absolutely all** devices of the area, enable the **👁 "Show all devices"** button in the header.
+By default only meaningful devices make it onto the plan: non-physical ones (service records, bridges, scenes, individual lamps folded into a light group) arrive with the **"Hide device from plan"** checkbox already ticked. The checkbox is yours from then on — every device dialog has it, virtual devices included. To see and un-hide them, open the device editor and press **"Show hidden"**: hidden devices appear as translucent blue ghosts, a click opens the dialog. Hidden devices still count toward the room's Zigbee signal, but cast no light.
 
 From here on you can just use the plan: clicking an icon opens the device card with the model, link and a button to jump into Home Assistant.
 
@@ -286,7 +286,7 @@ Services → House Plan**.
 
 **Do I need to write anything in YAML?** No. The only line is adding the card to the dashboard; everything else is done with the mouse.
 
-**My devices did not appear on the plan.** A device appears only if its Home Assistant area is bound to a drawn room. Check that the device has a room assigned (Settings → Devices) and that the room is outlined and bound to that area. If the device exists but is hidden by filtering (bridges, service records, duplicates) — enable the **👁 "Show all devices"** button in the header.
+**My devices did not appear on the plan.** A device appears only if its Home Assistant area is bound to a drawn room. Check that the device has a room assigned (Settings → Devices) and that the room is outlined and bound to that area. If the device exists but is hidden (the "Hide device from plan" checkbox — set automatically for bridges, scenes and other non-physical records) — open the device editor, press **"Show hidden"** and untick the box in its dialog.
 
 **Can I hide an unwanted device or rename it?** Yes — click the device on the plan and press "Edit" in its card: there you can change the name, icon, model or hide the icon.