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.

templates/podcast_types.go

@@ -0,0 +1,170 @@
+// Podcast template view types (plan task 1.9): the SSR shape shared by
+// the /podcasts page and the feed-detail page. The server formats
+// everything display-ready (dates in the requesting user's timezone —
+// D17; durations human) so templates stay logic-free.
+package templates
+
+import (
+	"fmt"
+	"strings"
+	"time"
+
+	"bookhoard/internal/utils"
+)
+
+// PodcastFeedCard is one grid card on /podcasts (or the hero on the
+// detail page).
+type PodcastFeedCard struct {
+	ID           string
+	LibraryID    string
+	Title        string
+	DisplayName  string // subscription-owned; renders instead of Title when set
+	Description  string
+	Host         string
+	Publisher    string
+	Language     string
+	Tags         []string
+	Explicit     bool
+	ArtworkPath  string
+	FeedType     string // serial | episodic
+	Medium       string
+	IsComplete   bool
+	FeedURL      string
+	LastFetched  string // display-formatted
+	SubscribedAt string
+
+	EpisodeTotal  int
+	DownloadedN   int
+	UndownloadedN int
+	NewEpisodes   bool
+
+	// Subscription-owned policy (detail page settings block).
+	AutoDownload      string
+	AutoDownloadCount int
+	Subscribed        bool
+}
+
+// DisplayTitle renders the subscription display name when set (D9).
+func (c PodcastFeedCard) DisplayTitle() string {
+	if c.DisplayName != "" {
+		return c.DisplayName
+	}
+	return c.Title
+}
+
+// TypeLabel renders the feed's shape for the card badge.
+func (c PodcastFeedCard) TypeLabel() string {
+	if c.FeedType == "serial" {
+		return "Serial"
+	}
+	if c.Medium != "" {
+		return strings.ToUpper(c.Medium[:1]) + c.Medium[1:]
+	}
+	return "Podcast"
+}
+
+// PodcastEpisodeRow is one episode-list line with the download
+// lifecycle inline (D8/D19: pending greyed + download button,
+// queued/downloading spinner, failed/rejected red + reason + retry).
+type PodcastEpisodeRow struct {
+	ID           string
+	FeedID       string
+	Title        string
+	Description  string
+	Date         string // display-formatted (user tz)
+	Position     int
+	Duration     string // human ("58:02" / "1:02:10")
+	Size         string // human MB/GB when known
+	PlayURL      string // reader URL (audio reader serves episodes like audiobooks)
+	CoverImage   string
+	ProgressPct  float64
+	Downloaded   bool
+	DownloadState string // pending|queued|downloading|downloaded|failed
+	DownloadError string
+}
+
+// StateBadge renders the canonical state label.
+func (r PodcastEpisodeRow) StateBadge() string {
+	switch r.DownloadState {
+	case "pending":
+		return "Not downloaded"
+	case "queued":
+		return "Queued"
+	case "downloading":
+		return "Downloading…"
+	case "failed":
+		return "Failed"
+	default:
+		return ""
+	}
+}
+
+// HasActiveDownloads: any episode queued/downloading — the partial
+// polls only while this is true (server-driven polling cadence).
+func HasActiveDownloads(rows []PodcastEpisodeRow) bool {
+	for _, r := range rows {
+		if r.DownloadState == "queued" || r.DownloadState == "downloading" {
+			return true
+		}
+	}
+	return false
+}
+
+// FormatEpisodeDuration renders seconds as H:MM:SS or M:SS.
+func FormatEpisodeDuration(seconds int) string {
+	if seconds <= 0 {
+		return ""
+	}
+	h := seconds / 3600
+	m := (seconds % 3600) / 60
+	s := seconds % 60
+	if h > 0 {
+		return fmt.Sprintf("%d:%02d:%02d", h, m, s)
+	}
+	return fmt.Sprintf("%d:%02d", m, s)
+}
+
+// FormatEpisodeSize renders bytes human (MB/GB).
+func FormatEpisodeSize(bytes int64) string {
+	switch {
+	case bytes <= 0:
+		return ""
+	case bytes >= 1<<30:
+		return fmt.Sprintf("%.1f GB", float64(bytes)/(1<<30))
+	default:
+		return fmt.Sprintf("%.1f MB", float64(bytes)/(1<<20))
+	}
+}
+
+// PodcastsPageData carries everything the /podcasts page renders.
+type PodcastsPageData struct {
+	Feeds      []PodcastFeedCard
+	Libraries  []LibraryData // podcasts-type libraries (add-feed targets)
+	Facets     map[string][]string
+	Query      string
+	ErrorMsg   string
+	HasLibrary bool
+}
+
+// PodcastDetailData carries the feed-detail page render.
+type PodcastDetailData struct {
+	Feed      PodcastFeedCard
+	Episodes  []PodcastEpisodeRow
+	GapCount  int
+	Order     string // native | oldest | newest (the caller's override)
+	IsAdmin   bool
+	IsSerial  bool // serial/audiobook feeds get the oldest-first suggestion (D5)
+}
+
+// podcastInt renders an int for templates.
+func podcastInt(n int) string {
+	return fmt.Sprintf("%d", n)
+}
+
+// timeStringPtr helper: display-format with empty fallback.
+func podcastTimeOrEmpty(t time.Time, valid bool, tz string) string {
+	if !valid || t.IsZero() {
+		return ""
+	}
+	return utils.FormatTimeInTimezone(t, tz)
+}