Remove unused recycle bin and add optional local file delete (#26)

Soft-delete restore/purge/list and the recycle_purge job are gone.
Admin delete now removes library index rows, with an optional
delete_files query that also deletes local media + sidecar NFO.
UI copy is renamed from 移入回收站 to 删除, with a confirm checkbox.

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: truewhile <truewhile@users.noreply.github.com>

internal/handler/media_delete_test.go

@@ -0,0 +1,23 @@
+package handler
+
+import "testing"
+
+func TestParseDeleteFilesQuery(t *testing.T) {
+	cases := []struct {
+		raw  string
+		want bool
+	}{
+		{"", false},
+		{"0", false},
+		{"false", false},
+		{"1", true},
+		{"true", true},
+		{"TRUE", true},
+		{"yes", true},
+	}
+	for _, tc := range cases {
+		if got := parseDeleteFilesQuery(tc.raw); got != tc.want {
+			t.Fatalf("parseDeleteFilesQuery(%q)=%v, want %v", tc.raw, got, tc.want)
+		}
+	}
+}