Add personalization, outbound feeds, and PWA/push to the web UI

A multi-session build turning Pete's read-only web UI into something people
return to. Five phases, signed-in features keyed off the OIDC subject; anonymous
visitors keep the reverse-chron feed and localStorage-only state.

Phase 1 — per-user read + bookmark state: user_story_state table +
storage/userstate.go; auth-gated /api/read, /api/bookmark, /api/state and a
/bookmarks page; reader.js syncs state server-side for signed-in users. Also
hides the Matrix-posting UI when posting.enabled=false (web-only mode).

Phase 2 — outbound feeds: storage.ListForFeed + web/feed.go hand-build RSS 2.0
(content:encoded) and JSON Feed 1.1 (no new dep); /feed.xml, /feed.json and
per-channel variants; <link rel=alternate> discovery tags.

Phase 3 — "For you" + related: storage/rank.go scores recent unread candidates
by channel/source affinity + recency decay; RelatedStories via FTS5. ForYou rail
+ /for-you page; public /api/related feeds the reader's "You might also like".

Phase 4 — source-health dashboard: source_health table + storage/sourcehealth.go
(RecordPollResult, ListSourceHealth, SourceContentStats), written by the poller;
admin-gated /status page behind web.admin_subs.

Phase 5 — PWA + offline reader + Web Push: root-scoped manifest.webmanifest and
sw.js (app-shell precache, /api/article runtime cache for offline reading,
offline fallback, push/notificationclick handlers); PNG icons from pete.avif;
pwa.js registers the SW and drives a notifications toggle. Web Push adds
webpush-go, a [web.push] config block (pete -genvapid mints VAPID keys), a
push_subscriptions table, auth-gated subscribe/unsubscribe endpoints, and a
digest sender that pings each subscriber "N new stories" past their watermark,
honoring disabled-sources and pruning gone endpoints.

Tests added beside each new storage/web file; go test ./... and go vet clean.

config.example.toml

@@ -37,6 +37,12 @@ listen_addr = ":8080"
 site_title = "Pete"
 base_url = "https://news.parodia.dev"
 
+# OIDC subjects allowed to view the owner-facing source-health dashboard at
+# /status (per-feed poll status, failures, content stats). Requires web.auth
+# below. Empty = /status returns 404 for everyone. Find a user's subject in the
+# server logs ("auth: user signed in" sub=...) after they sign in once.
+admin_subs = []
+
 # Optional OIDC sign-in (Authentik). When enabled, signed-in users get their
 # preferences (hidden feeds, weather location, toggles) stored server-side keyed
 # by their OIDC subject and synced across devices. Anonymous visitors keep using
@@ -53,6 +59,24 @@ redirect_url = "https://news.parodia.dev/auth/callback"
 # HMAC key that signs the session cookie. Generate with: openssl rand -hex 32
 session_secret = "${PETE_SESSION_SECRET}"
 
+# Optional Web Push digests. When enabled, signed-in users can opt in (from the
+# feed-settings panel) to a periodic "N new stories" notification, delivered via
+# a service worker so it also works when the site is installed as a PWA. Push is
+# signed-in only, so it needs web.auth above; it does nothing otherwise.
+# Generate the VAPID keypair once with:  pete -genvapid
+# then paste the two keys here (the private key is a secret — treat it like a
+# password). subject identifies you to the push service (a mailto: or https: URL).
+[web.push]
+enabled = false
+vapid_public_key = "${PETE_VAPID_PUBLIC_KEY}"
+vapid_private_key = "${PETE_VAPID_PRIVATE_KEY}"
+subject = "mailto:admin@parodia.dev"
+# How often the sender wakes to look for new stories per subscriber (minutes).
+interval_minutes = 360
+# Smallest number of new (non-hidden) stories that triggers a digest, so a lone
+# item doesn't ping everyone.
+min_stories = 3
+
 # Every enabled source MUST set direct_route to a key from [matrix.channels] above.
 # There is no automatic classification — Pete posts each story to its configured channel.
 # Optional: language = "en" drops feed items whose per-item <language> tag is