Fix(hacs): Raise minimum HA version to 2026.10.0

hacs.json still advertised Home Assistant 2026.4.0 while
pyproject.toml has required 2026.10.0 since #778, and the test suite
only runs against 2026.10.x. The HA 2026.11 Marketplace uses this
floor to decide which release to offer, so users on older cores were
offered releases the project does not test or support.

Also drop render_readme: it is not one of the keys the Marketplace
reads, so it is dead configuration.

Closes #883

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Signed-off-by: Andrew Grimberg <tykeal@bardicgrove.org>

hacs.json

@@ -2,6 +2,5 @@
   "name": "Rental Control",
   "zip_release": true,
   "filename": "rental_control.zip",
-  "homeassistant": "2026.4.0",
-  "render_readme": true
+  "homeassistant": "2026.10.0"
 }