refactor(document): introduce SearchFilters record (#683)

Filter-only value object bundling the ten search predicates so the long
positional argument lists on the document search chain can be replaced
with one named record — killing the sender/receiver and from/to swap-bug
class. Mirrors the existing DensityFilters; carries a withUndated copy
accessor for the forced-undated count path. Unused as of this commit.

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

backend/src/main/java/org/raddatz/familienarchiv/document/SearchFilters.java

@@ -0,0 +1,40 @@
+package org.raddatz.familienarchiv.document;
+
+import org.raddatz.familienarchiv.tag.TagOperator;
+
+import java.time.LocalDate;
+import java.util.List;
+import java.util.UUID;
+
+/**
+ * The filter predicates honoured by {@link DocumentService#searchDocuments} and
+ * {@link DocumentService#findIdsForFilter}. Sort, direction, and pagination are
+ * deliberately excluded — they are not filter predicates, and {@code findIdsForFilter}
+ * needs none of them; they are passed as separate arguments instead.
+ *
+ * Kept as a record so the ten values are passed as one named bundle instead of a
+ * positional argument list where two UUIDs (sender vs. receiver) or two dates
+ * (from vs. to) can be swapped by accident at the call site — a transposition that
+ * compiles cleanly and silently returns the wrong rows.
+ *
+ * Sibling of {@link DensityFilters} (= these fields minus from/to/undated); kept
+ * separate on purpose, so the density call path never reasons about date/undated
+ * fields it deliberately excludes.
+ */
+public record SearchFilters(
+        String text,
+        LocalDate from,
+        LocalDate to,
+        UUID sender,
+        UUID receiver,
+        List<String> tags,
+        String tagQ,
+        DocumentStatus status,
+        TagOperator tagOperator,
+        boolean undated) {
+
+    /** Returns a copy with {@code undated} overridden — used by the undated-count path. */
+    public SearchFilters withUndated(boolean undated) {
+        return new SearchFilters(text, from, to, sender, receiver, tags, tagQ, status, tagOperator, undated);
+    }
+}