feat(podcasts): unset listening order defaults to reversed (audiobook-first)

The per-feed listening order — the Order dropdown on the podcast page
and player — resolved its UNSET state to "native": feed document order,
which runs newest-first for classic RSS. This platform is audiobook-
first, so native started every book at its LAST chapter (verified on
live data: 7th Son position 1 = Bonus Episode #2, positions descending
through the chapters).

The unset fallback flips to "reverse" at every resolution site of that
ONE setting — the podcast page's list + dropdown (podcastOrderForFeed),
the player's feed chain (reader.go), and the download queue
(orderOverrideFor) — so the dropdown shows reversed selected, the page
renders in that order, and play/download follow. Stored overrides are
untouched (native stays a valid savable choice); no ordering semantics
changed; collections are untouched.

Pins: the flipped native expectation is changelogged in contract_pins;
new pins cover the sequence config carrying reverse, feed position 1
playing last, and the page dropdown rendering reverse selected for an
unset feed.

internal/router/reader.go

@@ -187,8 +187,11 @@ func buildPodcastSequenceContext(c *echo.Context, cfg *Config, item *database.Me
 		return nil
 	}
 
-	// Effective order override (D5): reader_settings KV.
-	order := "native"
+	// Effective order override (D5): reader_settings KV. UNSET defaults
+	// to "reverse" (2026-11-01: audiobook-first — native document order
+	// starts a book at its last chapter); the same default the podcast
+	// page's Order dropdown shows. Stored overrides are untouched.
+	order := "reverse"
 	if row, err := cfg.Queries.GetUserSettingByKey(ctx, database.GetUserSettingByKeyParams{
 		UserID:     userID,
 		SettingKey: "podcast_order:" + uuid.UUID(item.SourceFeedID.Bytes).String(),