v1.46.5: audit of every automatic deletion

Owner's decision after the incident: a detached plan is never deleted, at any
age. v1.46.4 gave it a month; this makes it permanent and, more importantly,
writes the reasoning where the next change will trip over it — docs/SCOPE.md now
carries the standing rule. The component may delete a file only when a user
action says so. 'Nothing points at this any more' is not such an action, because
the two errors are not symmetrical: wasted disk is visible, cheap and
reversible; a deleted file is none of those.

Went through every other automatic deletion with the same question. One more
was wrong: houseplan/files/cleanup rmtree'd whatever folder the card named. A
partial migration leaves urls pointing into it — files/migrate deliberately does
not rewrite the ones it could not confirm — so those were live links to files
being deleted; and a wrong or stale id from any client destroyed a live device's
manuals. The server now reads the stored config under its lock and removes only
what nothing references, keeping the rest and saying so.

Also: a plan of a DELETED space now waits thirty days rather than an hour.
Deleting a space is deliberate; an hour is a short window to notice a misclick.

The rest came out clean: layout/delete and marker/room/space removal are all
confirm-guarded user actions, upload temporaries are never user-visible, and
dropping legacy 'segments' is a documented migration.

custom_components/houseplan/manifest.json

@@ -16,5 +16,5 @@
   "issue_tracker": "https://github.com/Matysh/houseplan-card/issues",
   "requirements": [],
   "single_config_entry": true,
-  "version": "1.46.4"
+  "version": "1.46.5"
 }