fix v1.44.2: external review CR-1..CR-3

CR-1: the lock invariant is restated precisely (never by an accidental
tap; the door card's labeled button is the ONE sanctioned surface),
unlocking now confirms, and smoke_lock_invariant exercises all five
actuation paths (icon tap, controls[], card entities, _cardToggle,
opening card).

CR-2: attachment migration is transactional — the server COPIES files,
the config is committed with its revision check, and only then the old
folder is removed via the new houseplan/files/cleanup. A rejected save
no longer leaves the stored urls pointing at an emptied folder.

CR-3: migrate returns an exact {source: written} mapping; only confirmed
copies are rewritten, destination name collisions get a unique name
instead of silently linking a pre-existing file, and a failed migration
raises a toast instead of being swallowed.

+1 unit test (119), +1 backend test, +1 smoke (51 total); docs
same-commit

docs/TESTING.md

@@ -40,6 +40,16 @@
       below; config/diagnostic entities are not listed; locks never toggle from
       the card [auto: smoke_card_controls]
 
+- [ ] Lock invariant, all paths (v1.44.2, review CR-1): icon tap, controls[],
+      device card and _cardToggle refuse locks/alarm panels entirely; the door
+      card's Unlock asks for confirmation, Lock does not [auto: smoke_lock_invariant]
+- [ ] Attachment migration is transactional (v1.44.2, review CR-2/CR-3):
+      rebinding COPIES files, saves the config, and only then deletes the old
+      folder; a rejected save leaves the old files and urls intact; a name
+      collision in the destination gets a unique name (the pre-existing file is
+      never silently linked); urls are rewritten only for confirmed copies
+      [auto: unit logic.test + tests_backend]
+
 ## Environments matrix
 
 Run the *core flows* (marked ★ below) in each environment at least once per minor release: