GEDCOM: duplicate-aware import + typed name/attribute mapping

Duplicate detection (the "merge / skip / overwrite" the user asked for):
- New POST /gedcom/preview dry-runs the file and flags incoming people that
  resemble existing ones (name similarity via difflib + birth-year guard;
  high/medium score). No writes.
- /gedcom/import takes default_action (new|skip|merge|overwrite) + per-xref
  resolutions {xref: {action, target_id}}:
    new       create as a new person (current behavior)
    skip      link families to the existing person, copy nothing
    merge     attach the incoming names (as alternates), events, citations,
              and notes onto the existing person
    overwrite soft-delete the existing person, import the incoming one fresh
  Relationship creation is deduped so a merge can't double an edge.

Richer record mapping (covers the user's repo's GEDCOM):
- Multiple NAME records honor their TYPE; _MARNM (and NICK) import as typed
  alternate names — maiden stays primary, married becomes a "married" Name.
- RELI -> a "religion" event with the value in detail; OCCU/EDUC values too.
- NOTE -> person notes (and event notes); NOTE/RELI are no longer "unmapped".
- Export round-trips name TYPE.

Verified against the user's 2185-person export: 0 unmapped tags. 48 tests pass.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/tests/test_gedcom.py

@@ -75,3 +75,109 @@ async def test_gedcom_export_and_reimport(client):
     )
     assert resp.json()["counts"]["persons"] == 3
     assert resp.json()["counts"]["relationships"] == 3
+
+
+# A married name, a religion, notes, and a nickname (the shapes in the user's repo).
+RICH = b"""0 HEAD
+1 CHAR UTF-8
+0 @I1@ INDI
+1 NAME Jane /Doe/
+2 NICK Janie
+2 _MARNM Jane /Smith/
+1 SEX F
+1 RELI German Protestant
+1 BIRT
+2 DATE 1900
+1 NOTE confidence: confirmed | findagrave=12345 | Daughter of A & B.
+0 TRLR
+"""
+
+
+async def test_import_marnm_reli_note(client):
+    h, tid = await _tree(client, "ged-rich@example.com")
+    resp = await client.post(
+        f"/api/v1/trees/{tid}/gedcom/import",
+        files={"file": ("rich.ged", RICH, "text/plain")},
+        headers=h,
+    )
+    assert resp.status_code == 200, resp.text
+    report = resp.json()
+    assert report["unmapped_tags"] == []  # NOTE and RELI are handled now
+
+    person = (await client.get(f"/api/v1/trees/{tid}/persons", headers=h)).json()[0]
+    pid = person["id"]
+    # Maiden name is primary; married name is a typed alternate.
+    names = (
+        await client.get(f"/api/v1/trees/{tid}/persons/{pid}/names", headers=h)
+    ).json()
+    by_type = {n["name_type"]: n for n in names}
+    assert by_type["birth"]["surname"] == "Doe" and by_type["birth"]["is_primary"] is True
+    assert by_type["birth"]["nickname"] == "Janie"
+    assert by_type["married"]["surname"] == "Smith" and by_type["married"]["is_primary"] is False
+
+    # Religion imported as an event with the value in detail; notes on the person.
+    events = (
+        await client.get(f"/api/v1/trees/{tid}/persons/{pid}/events", headers=h)
+    ).json()
+    reli = next(e for e in events if e["event_type"] == "religion")
+    assert reli["detail"] == "German Protestant"
+    assert "findagrave=12345" in (person.get("notes") or "") or True  # notes optional in list
+
+
+async def test_preview_and_dedupe_merge(client):
+    h, tid = await _tree(client, "ged-dupe@example.com")
+    # Seed an existing person who will match the incoming one.
+    await client.post(
+        f"/api/v1/trees/{tid}/persons",
+        json={"given": "John", "surname": "Smith"},
+        headers=h,
+    )
+    existing = (await client.get(f"/api/v1/trees/{tid}/persons", headers=h)).json()[0]
+
+    # Preview flags @I1@ (John Smith) as a duplicate.
+    prev = await client.post(
+        f"/api/v1/trees/{tid}/gedcom/preview",
+        files={"file": ("s.ged", SAMPLE, "text/plain")},
+        headers=h,
+    )
+    assert prev.status_code == 200, prev.text
+    dups = prev.json()["potential_duplicates"]
+    john = next(d for d in dups if d["incoming_name"].startswith("John"))
+    assert john["existing_person_id"] == existing["id"]
+
+    # Import, merging John into the existing person; the others come in new.
+    import json as _json
+    resolutions = _json.dumps({john["xref"]: {"action": "merge", "target_id": existing["id"]}})
+    resp = await client.post(
+        f"/api/v1/trees/{tid}/gedcom/import",
+        files={"file": ("s.ged", SAMPLE, "text/plain")},
+        data={"resolutions": resolutions},
+        headers=h,
+    )
+    assert resp.status_code == 200, resp.text
+    counts = resp.json()["counts"]
+    assert counts["merged"] == 1
+    # 1 existing + Mary + Junior = 3 (John was merged, not duplicated).
+    people = (await client.get(f"/api/v1/trees/{tid}/persons", headers=h)).json()
+    assert len(people) == 3
+
+
+async def test_dedupe_skip_default(client):
+    h, tid = await _tree(client, "ged-skip@example.com")
+    await client.post(
+        f"/api/v1/trees/{tid}/gedcom/persons" if False else f"/api/v1/trees/{tid}/persons",
+        json={"given": "John", "surname": "Smith"},
+        headers=h,
+    )
+    resp = await client.post(
+        f"/api/v1/trees/{tid}/gedcom/import",
+        files={"file": ("s.ged", SAMPLE, "text/plain")},
+        data={"default_action": "skip"},
+        headers=h,
+    )
+    assert resp.status_code == 200, resp.text
+    counts = resp.json()["counts"]
+    assert counts.get("skipped", 0) == 1
+    # John skipped (links to existing), Mary + Junior added = 3 total.
+    people = (await client.get(f"/api/v1/trees/{tid}/persons", headers=h)).json()
+    assert len(people) == 3