feat(search): add SearchMatchData record for per-document match signals

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/main/java/org/raddatz/familienarchiv/dto/SearchMatchData.java

@@ -0,0 +1,48 @@
+package org.raddatz.familienarchiv.dto;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+
+import java.util.List;
+import java.util.UUID;
+
+/**
+ * Match signals for a single document in a full-text search result.
+ * All fields are non-null except {@code transcriptionSnippet}, which is null
+ * when no transcription block matched the query.
+ */
+public record SearchMatchData(
+        /**
+         * Best-ranked matching transcription line, or null if no block matched.
+         */
+        String transcriptionSnippet,
+
+        /**
+         * Character offsets of highlighted terms within the document title.
+         * Empty when the title did not contribute to the match.
+         */
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+        List<MatchOffset> titleOffsets,
+
+        /**
+         * True when the sender's name matched the query.
+         */
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+        boolean senderMatched,
+
+        /**
+         * IDs of receiver persons whose names matched the query.
+         */
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+        List<UUID> matchedReceiverIds,
+
+        /**
+         * IDs of tags whose names matched the query.
+         */
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+        List<UUID> matchedTagIds
+) {
+    /** Canonical "no match data" value for a single document. */
+    public static SearchMatchData empty() {
+        return new SearchMatchData(null, List.of(), false, List.of(), List.of());
+    }
+}

backend/src/test/java/org/raddatz/familienarchiv/dto/SearchMatchDataTest.java

@@ -0,0 +1,44 @@
+package org.raddatz.familienarchiv.dto;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class SearchMatchDataTest {
+
+    @Test
+    void transcription_snippet_is_nullable() {
+        SearchMatchData data = new SearchMatchData(null, List.of(), false, List.of(), List.of());
+
+        assertThat(data.transcriptionSnippet()).isNull();
+    }
+
+    @Test
+    void non_null_list_fields_are_empty_by_default_in_empty_factory() {
+        SearchMatchData data = SearchMatchData.empty();
+
+        assertThat(data.transcriptionSnippet()).isNull();
+        assertThat(data.titleOffsets()).isEmpty();
+        assertThat(data.matchedReceiverIds()).isEmpty();
+        assertThat(data.matchedTagIds()).isEmpty();
+        assertThat(data.senderMatched()).isFalse();
+    }
+
+    @Test
+    void holds_all_field_values() {
+        MatchOffset offset = new MatchOffset(0, 4);
+        SearchMatchData data = new SearchMatchData(
+                "schreibt dir aus dem Feld",
+                List.of(offset),
+                true,
+                List.of(),
+                List.of()
+        );
+
+        assertThat(data.transcriptionSnippet()).isEqualTo("schreibt dir aus dem Feld");
+        assertThat(data.titleOffsets()).containsExactly(offset);
+        assertThat(data.senderMatched()).isTrue();
+    }
+}