feat(content): seller-picked payment methods + music always in the bottom bar + video PiP

- Paid sharing: AccessControl::Paid gains an accepted-methods list
  (lightning/onchain/ecash/fedimint; empty = all, back-compat). Sellers pick
  methods in ShareModal, gated on what the node can actually receive (LND
  running/channel open, ecash wallet, fedimint joined) with an ⓘ that
  explains exactly how to enable a missing rail. Enforced server-side (the
  invoice/onchain mints refuse non-accepted methods; the serve gate only
  honors tokens/hashes for accepted rails) and the buyer's pay modal only
  offers what the seller accepts.
- Purchased music: the two remaining lightbox paths now use the bottom-bar
  player — the immediate post-ecash-purchase viewer and the Paid Files
  tab's window.open.
- Picture-in-picture buttons on the peer video player and the cloud media
  lightbox (utils/pip.ts; Chromium/Safari, no-op elsewhere).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

core/archipelago/src/content_server.rs

@@ -51,9 +51,25 @@ pub enum AccessControl {
     PeersOnly,
     Paid {
         price_sats: u64,
+        /// Payment methods the sharer accepts: "lightning", "onchain",
+        /// "ecash", "fedimint". Empty = everything — which is also what
+        /// catalogs written before this field deserialize to.
+        #[serde(default, skip_serializing_if = "Vec::is_empty")]
+        accepted: Vec<String>,
     },
 }
 
+/// Does the sharer accept this payment method for the item? Empty list =
+/// all methods (pre-field catalogs and "no preference").
+pub fn method_accepted(access: &AccessControl, method: &str) -> bool {
+    match access {
+        AccessControl::Paid { accepted, .. } => {
+            accepted.is_empty() || accepted.iter().any(|m| m == method)
+        }
+        _ => true,
+    }
+}
+
 #[derive(Debug, Default, Serialize, Deserialize)]
 pub struct ContentCatalog {
     pub items: Vec<ContentItem>,
@@ -269,20 +285,26 @@ pub async fn serve_content(
 
     // Check access control
     match &item.access {
-        AccessControl::Paid { price_sats } => {
+        AccessControl::Paid { price_sats, .. } => {
             // Two ways to satisfy payment:
             //  (a) a valid ecash token (the local-wallet fast path), or
             //  (b) a Lightning-invoice payment hash this node issued and has
             //      since confirmed settled (the "pay from any wallet" path, #46).
+            // Each path only counts when the sharer accepts that method.
             let mut authorized = false;
             if let Some(token) = payment_token {
-                if verify_payment_token(data_dir, token, *price_sats).await {
+                if (method_accepted(&item.access, "ecash")
+                    || method_accepted(&item.access, "fedimint"))
+                    && verify_payment_token(data_dir, token, *price_sats).await
+                {
                     authorized = true;
                 }
             }
             if !authorized {
                 if let Some(hash) = invoice_hash {
-                    if crate::content_invoice::is_paid_for(hash, id).await {
+                    if method_accepted(&item.access, "lightning")
+                        && crate::content_invoice::is_paid_for(hash, id).await
+                    {
                         authorized = true;
                     }
                 }