feat(crm): contact email & person-opportunity indexes, history entity whitelist

- BuildContactEmailIndex: one-pass email→contact id map over all persons
  (O(N) instead of per-address FindPersonByEmail O(N×M))
- BuildPersonOpportunityIndex: person→lowest-id opportunity for history notes
  (OO has no person-level history; verified live)
- HistoryEntity{Opportunity,Case} whitelist constants
- IsCompany/ContactID/NumericIDLess/SortIDs helpers with unit tests

contact_indexes_test.go

@@ -0,0 +1,65 @@
+package onlyoffice
+
+import "testing"
+
+func TestIsCompany(t *testing.T) {
+	if IsCompany(map[string]any{"isCompany": true}) != true {
+		t.Fatal("true row not detected")
+	}
+	if IsCompany(map[string]any{"isCompany": false}) {
+		t.Fatal("false row detected as company")
+	}
+	if IsCompany(map[string]any{}) {
+		t.Fatal("missing field detected as company")
+	}
+	if IsCompany(nil) {
+		t.Fatal("nil row detected as company")
+	}
+}
+
+func TestNumericIDLess(t *testing.T) {
+	cases := []struct {
+		a, b string
+		want bool
+	}{
+		{"9", "10", true},
+		{"1747", "1748", true},
+		{"abc", "abd", true},
+		{"10", "9", false},
+		{" 12 ", "13", true},
+		{"x1", "2", false}, // non-numeric falls back lexical: "x1" > "2"
+	}
+	for _, c := range cases {
+		if got := NumericIDLess(c.a, c.b); got != c.want {
+			t.Errorf("NumericIDLess(%q,%q)=%v want %v", c.a, c.b, got, c.want)
+		}
+	}
+}
+
+func TestSortIDs(t *testing.T) {
+	ids := []string{"20", "3", "100", "1"}
+	SortIDs(ids)
+	want := "1 3 20 100"
+	got := ""
+	for i, id := range ids {
+		if i > 0 {
+			got += " "
+		}
+		got += id
+	}
+	if got != want {
+		t.Fatalf("SortIDs=%q want %q", got, want)
+	}
+}
+
+func TestContactID(t *testing.T) {
+	if ContactID(map[string]any{"id": float64(42)}) != "42" {
+		t.Fatal("numeric id formatting broken")
+	}
+}
+
+func TestHistoryEntityConstants(t *testing.T) {
+	if HistoryEntityOpportunity != "opportunity" || HistoryEntityCase != "case" {
+		t.Fatal("history entity whitelist drifted from live-verified values")
+	}
+}