feat(podcasts): web UI — /podcasts page, feed detail, download lifecycle (task 1.9)

Rendering ownership holds throughout: every piece of server data is
templ-rendered; htmx swaps partials; the only TS is the Add-Feed modal
toggle + error surfacing (pure client-local state, bundled via
web/src/podcasts.ts with automatic bundle-hash stamping).

Sidebar: /podcasts nav entry (D13, between Series and Collections),
gated by a ShowPodcastsNav flag resolved centrally in
getTemplateUserWithTheme (one indexed COUNT — same class of
per-request lookup as the live-user guard). New 'podcast' icon.

/podcasts: header + Add Feed modal (htmx post → HX-Redirect to the
feed page; inline error surfacing on failure), subscription-scoped
search + facet bar (host/tag/language — server-side GET filters, no
JS), grid cards with download counts / new-episodes / complete /
explicit badges. Empty states for no-library (admin creates it first)
and no-subscriptions.

Feed detail: hero (artwork, host/publisher, tags, fetch state), action
row — Download All, Refresh, ORDER SELECTOR (D5 override), serial
one-click oldest-first suggestion (never silent), auto-download policy
select (D6), Unsubscribe (files retained), admin Remove Feed — gap
banner (D8 count), and the EPISODE LIST with the full lifecycle inline
(D8/D19): pending greyed + Download button (every non-downloaded
episode has one), queued/downloading pulse, failed RED + reason text +
Retry (same endpoint). The list is a self-refreshing partial: re-fetch
on the podcast:changed HX-Trigger and polls every 4s ONLY while the
server says downloads are active (it renders the polling variant).

API endpoints grew HX awareness: 204 + HX-Trigger podcast:changed (or
HX-Redirect for add/unsubscribe/remove) — the sanctioned Go-handler
response channels; JSON callers keep JSON. AddFeed result exposes the
fetch-error text for the redirect.

Dates render in the requesting user's timezone (D17) via
utils.FormatTimeInTimezone; episodes play through the existing
/readers/{id} audio reader (episodes ARE audiobook items — no new
player code day one). CSP tripwire (templates/csp_source_test.go)
passes: no inline scripts, no on*= handlers, no hx-on/js: vals.

internal/handlers/podcast.go

@@ -33,21 +33,39 @@ func NewPodcastHandler(db *database.Queries, svc *services.PodcastService, worke
 // ---- request/response shapes ----
 
 type AddPodcastFeedRequest struct {
-	LibraryID   string `json:"library_id" validate:"required"`
-	URL         string `json:"url" validate:"required"`
-	DownloadAll bool   `json:"download_all"`
+	LibraryID   string `json:"library_id" form:"library_id" validate:"required"`
+	URL         string `json:"url" form:"url" validate:"required"`
+	DownloadAll bool   `json:"download_all" form:"download_all"`
 }
 
 type UpdatePodcastSubscriptionRequest struct {
-	DisplayName       *string `json:"display_name"`
-	AutoDownload      *string `json:"auto_download" validate:"omitempty,oneof=off all newest"`
-	AutoDownloadCount *int    `json:"auto_download_count"`
+	DisplayName       *string `json:"display_name" form:"display_name"`
+	AutoDownload      *string `json:"auto_download" form:"auto_download" validate:"omitempty,oneof=off all newest"`
+	AutoDownloadCount *int    `json:"auto_download_count" form:"auto_download_count"`
 }
 
 type DownloadEpisodesRequest struct {
 	EpisodeIDs []string `json:"episode_ids"`
 }
 
+// hxAccepted answers an htmx request with 204 + the podcast:changed
+// trigger — the episode-list partial re-fetches itself (its hx-trigger
+// listens for the event; polling covers download progress). JSON
+// callers keep the JSON body. HX-Redirect/HX-Trigger headers are the
+// sanctioned Go-handler response channels (CSP discipline).
+func hxAccepted(c *echo.Context, redirect string) error {
+	if redirect != "" {
+		c.Response().Header().Set("HX-Redirect", redirect)
+		return c.NoContent(http.StatusNoContent)
+	}
+	c.Response().Header().Set("HX-Trigger", "podcast:changed")
+	return c.NoContent(http.StatusNoContent)
+}
+
+func isHXRequest(c *echo.Context) bool {
+	return c.Request().Header.Get("HX-Request") == "true"
+}
+
 // podcastErrorResponse maps service errors (incl. PodcastError statuses)
 // onto HTTP responses.
 func podcastErrorResponse(c *echo.Context, err error) error {
@@ -94,6 +112,14 @@ func (h *PodcastHandler) AddFeed(c *echo.Context) error {
 			// episode list states.
 		}
 	}
+	if isHXRequest(c) {
+		// Post-redirect-get: land on the new feed's page. Fetch errors
+		// (subscription stands) surface via the flash query param.
+		if res.FeedError() != "" {
+			return hxAccepted(c, "/podcasts/"+uuidString(res.Feed.ID)+"?fetch_error=1")
+		}
+		return hxAccepted(c, "/podcasts/"+uuidString(res.Feed.ID))
+	}
 	return c.JSON(http.StatusCreated, res)
 }
 
@@ -223,6 +249,11 @@ func (h *PodcastHandler) UpdateSubscription(c *echo.Context) error {
 	if err != nil {
 		return podcastErrorResponse(c, err)
 	}
+	if isHXRequest(c) {
+		// Policy changes feed the auto-download union on the next poll.
+		_, _ = h.worker.ApplyAutoPolicies(ctx, feedID)
+		return hxAccepted(c, "")
+	}
 	return c.JSON(http.StatusOK, updated)
 }
 
@@ -242,6 +273,9 @@ func (h *PodcastHandler) DeleteSubscription(c *echo.Context) error {
 	if rows == 0 {
 		return c.JSON(http.StatusNotFound, map[string]string{"error": "not subscribed"})
 	}
+	if isHXRequest(c) {
+		return hxAccepted(c, "/podcasts")
+	}
 	return c.JSON(http.StatusOK, map[string]string{"message": "unsubscribed (files retained)"})
 }
 
@@ -256,6 +290,9 @@ func (h *PodcastHandler) RefreshFeed(c *echo.Context) error {
 	if err := h.podcasts.RefreshFeed(c.Request().Context(), feedID); err != nil {
 		return podcastErrorResponse(c, err)
 	}
+	if isHXRequest(c) {
+		return hxAccepted(c, "")
+	}
 	return c.JSON(http.StatusOK, map[string]string{"message": "refreshed"})
 }
 
@@ -301,6 +338,9 @@ func (h *PodcastHandler) DownloadEpisodes(c *echo.Context) error {
 		if err != nil {
 			return podcastErrorResponse(c, err)
 		}
+		if isHXRequest(c) {
+			return hxAccepted(c, "")
+		}
 		return c.JSON(http.StatusAccepted, map[string]interface{}{"queued": queued})
 	}
 	epID, err := parseUUID(eidRaw)
@@ -310,6 +350,9 @@ func (h *PodcastHandler) DownloadEpisodes(c *echo.Context) error {
 	if err := h.worker.QueueEpisode(ctx, epID, feedID); err != nil {
 		return podcastErrorResponse(c, err)
 	}
+	if isHXRequest(c) {
+		return hxAccepted(c, "")
+	}
 	return c.JSON(http.StatusAccepted, map[string]string{"message": "queued"})
 }
 
@@ -367,6 +410,9 @@ func (h *PodcastHandler) DeleteFeed(c *echo.Context) error {
 	} else if rows == 0 {
 		return c.JSON(http.StatusNotFound, map[string]string{"error": "feed not found"})
 	}
+	if isHXRequest(c) {
+		return hxAccepted(c, "/podcasts")
+	}
 	return c.JSON(http.StatusOK, map[string]string{"message": "feed removed"})
 }
 
@@ -438,6 +484,9 @@ func (h *PodcastHandler) SetFeedOrder(c *echo.Context) error {
 			return podcastErrorResponse(c, err)
 		}
 	}
+	if isHXRequest(c) {
+		return hxAccepted(c, "")
+	}
 	return c.JSON(http.StatusOK, map[string]string{"order": req.Order})
 }