Store a target's settings as columns (closes #543)

A target's settings move from the per-type JSON string in
targets.config to columns: url, headers, timeout_seconds,
forward_query, archive_expiry and archive_rotation. A column a type
does not use stays empty. headers holds the header map as JSON text
through GORM's JSON serializer, and archive_expiry holds a
time.Duration, 0 meaning never. The forms check each setting once,
with the same refusals and messages, and the edit form is filled from
the columns, so the per-type config structs, their parsers and the
"could not be read" branches are gone. A delivery task carries the
six settings in place of the JSON string; tests check that each copy
into a task, and back out of one, keeps all six.

Model: opus-5-5

internal/archive/sweeper.go

@@ -199,22 +199,11 @@ func (s *Sweeper) sweep(ctx context.Context) {
 	}
 }
 
-// sweepTarget prunes the archive of a single database target.
-// A missing, empty, or "never" expiry parses as a zero duration
-// and is skipped entirely, so those archives are never pruned.
+// sweepTarget prunes the archive of a single database target. A
+// target with an ArchiveExpiry of 0 keeps its archive forever and is
+// skipped entirely, so that archive is never pruned.
 func (s *Sweeper) sweepTarget(target *database.Target) {
-	expiry, err := ParseExpiry(target.Config)
-	if err != nil {
-		s.log.Error(
-			"archive sweep: invalid database target config",
-			"webhook_id", target.WebhookID,
-			"target_id", target.ID,
-			"error", err,
-		)
-
-		return
-	}
-
+	expiry := target.ArchiveExpiry
 	if expiry <= 0 {
 		return
 	}
@@ -223,7 +212,7 @@ func (s *Sweeper) sweepTarget(target *database.Target) {
 		return
 	}
 
-	err = s.writers.sweepArchive(target.ID, expiry)
+	err := s.writers.sweepArchive(target.ID, expiry)
 	if err == nil {
 		return
 	}