test(importing): verify re-import pruning and provisional precedence on real Postgres

Add a Testcontainers test that re-imports a document with a receiver and a tag
removed from the canonical row and asserts both links are pruned. Add a test that a
register person referenced by a document row is never flipped to provisional,
regardless of re-import, since the orchestrator loads the register/tree before
documents and the monotonic-downward guard prevents a flip. Pin that cross-loader
precedence in a mergeCanonical comment.

Refs #669

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/src/main/java/org/raddatz/familienarchiv/person/PersonService.java

@@ -168,7 +168,12 @@ public class PersonService {
         if (cmd.personType() != null && existing.getPersonType() == PersonType.PERSON) {
             existing.setPersonType(cmd.personType());
         }
-        // provisional is monotonic: once a human confirms a person (false) it never reverts.
+        // provisional is monotonic-downward: once it is false it never reverts to true.
+        // This also pins the cross-loader precedence (ADR-025): a register/tree person is
+        // loaded before documents and already false, so a later document row that references
+        // the same source_ref (provisional=true) can never flip it provisional — the guard
+        // below only fires while existing is still provisional. Order of document rows is
+        // therefore irrelevant.
         if (existing.isProvisional()) {
             existing.setProvisional(cmd.provisional());
         }