Buildings and levels for the floor map, and make every identifier searchable

README.md

@@ -187,6 +187,29 @@ example of the whole sequence.
 
 For every environment variable and Setting key see the CONFIG page in the project wiki.
 
+### What the Windows installer requires
+
+The installer checks all of this before it changes anything and refuses rather
+than half-installing.
+
+| | Minimum | Notes |
+|---|---|---|
+| Windows Server | **2019** (build 10.0.17763) | Ships **IIS 10.0**, which is therefore the earliest IIS supported. Server 2016 is also IIS 10.0 but falls below the build floor and is refused. |
+| Windows client (test boxes) | **10 22H2** (build 10.0.19045) or 11 | **Pro or higher** - Home has no IIS at all. |
+| Architecture | 64-bit | The payload is cp314 win_amd64. |
+| IIS Web Server role | installed beforehand | `Install-WindowsFeature -Name Web-Server -IncludeManagementTools`. Needs no internet. |
+| Free disk | 5 GB | Refused below this. 40 GB is comfortable once uploads and config backups accumulate. |
+| Database | bundled MySQL 8.4 LTS, or your own | Bring credentials if you use an existing server. |
+
+The binding constraint is the operating system rather than IIS: the payload is
+Python 3.14 plus HttpPlatformHandler and URL Rewrite, and the handler itself runs
+on older IIS. An older host is untested rather than known-broken.
+
+If you must deploy onto something older, the INSTALL-WINDOWS-IIS page in the project wiki
+is the manual procedure and has no OS gate - it even documents MySQL 5.6, which is
+that era of machine. The trade is stated there: it produces a server the
+installer will not subsequently upgrade.
+
 ## Configuration
 
 Environment variables (`.env`):