Prepare v1.73.0-beta.9

Version fields and generated bundles move to 1.73.0-beta.9; the #506
changelog entry leaves Unreleased for the beta.9 section; release notes and
STATUS describe the startup-regression fix that unblocks the stable
promotion. No product change beyond #506, already reviewed and merged.

Issue: #506
User-Visible: no
Release: v1.73.0-beta.9

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "houseplan-card",
-  "version": "1.73.0",
+  "version": "1.73.0-beta.9",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "houseplan-card",
-      "version": "1.73.0",
+      "version": "1.73.0-beta.9",
       "license": "MIT",
       "dependencies": {
         "lit": "^3.1.3",