Share a feed, an item or a file (#48)

A share button in the feed's header, beside an item's "Open the original", and on each file.
It uses the Web Share API where the browser has it, which is the share sheet on a phone, and
copies the link where it does not. A file is shared by the publisher's address, not /media/,
which only someone signed in here can open.

Paid feeds carry the subscriber's access in their address, Patreon's in a token, so sharing one
gives the subscription away. An address that looks like that asks first.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/items.ts

@@ -249,7 +249,8 @@ function showDetail(e){
       <button class="btn ico" data-a="flag" title="${e.flagged?'Pinned: never deleted. Unpin':'Pin, so it is never deleted'}"
         aria-label="${e.flagged?'Unpin':'Pin'}">${e.flagged?ICON.pinOn:ICON.pin}</button>
       ${e.link?`<a class="btn ico" href="${esc(e.link)}" target="_blank" rel="noopener noreferrer"
-        title="Open the original" aria-label="Open the original">${ICON.open}</a>`:''}
+        title="Open the original" aria-label="Open the original">${ICON.open}</a>
+      <button class="btn ico" data-a="share" title="Share" aria-label="Share">${ICON.share}</button>`:''}
     </div>
     ${narrow?encs:''}
     <div class="dbody">${(e.description&&e.description.trim())||'<em>No show notes.</em>'}</div>`;
@@ -273,6 +274,8 @@ function encBox(x){
     : 'Delete file';
   const delBtn=`<button class="btn ico danger" data-a="del" data-enc="${x.id}" title="${delLabel}" aria-label="${delLabel}">${ICON.trash}</button>`;
   const saveBtn=`<a class="btn ico" href="/media/${x.id}" download title="Save to this computer" aria-label="Save to this computer">${ICON.save}</a>`;
+  // The publisher's address, not this server's copy, which only someone signed in here can open.
+  const shareBtn=`<button class="btn ico" data-a="share" data-enc="${x.id}" title="Share the file" aria-label="Share the file">${ICON.share}</button>`;
   if(x.path && !isPlayable(x)){
     // On disk, but not audio or video: view it, keep it, or remove it -- no player.
     return `<div class="encbox">
@@ -280,6 +283,7 @@ function encBox(x){
       <span class="meta" style="flex:1">${size}</span>
       <a class="btn ico" href="/media/${x.id}" target="_blank" rel="noopener noreferrer" title="View in a new tab" aria-label="View in a new tab">${ICON.open}</a>
       ${saveBtn}
+      ${shareBtn}
       ${delBtn}
     </div>`;
   }
@@ -291,6 +295,7 @@ function encBox(x){
       <span class="meta" style="flex:1">${size}</span>
       <button class="btn ico" data-a="play" data-enc="${x.id}" title="Play" aria-label="Play">${ICON.play}</button>
       ${saveBtn}
+      ${shareBtn}
       ${delBtn}
     </div>`;
   }
@@ -303,6 +308,7 @@ function encBox(x){
     <span class="meta" style="flex:1">${size}</span>
     ${x.state==='error'&&x.last_error?`<span class="err">${esc(x.last_error)}</span>`:''}
     ${viewable?`<a class="btn ico" href="${esc(x.url)}" target="_blank" rel="noopener noreferrer" title="View in a new tab" aria-label="View in a new tab">${ICON.open}</a>`:''}
+    ${shareBtn}
     <button class="btn ico" data-a="get" data-enc="${x.id}" title="Download to the server" aria-label="Download to the server">${ICON.download}</button>
   </div>`;
 }
@@ -314,6 +320,7 @@ async function epAction(a: string, e, el, encId?: number){
   const path=`/api/entries/${encodeURIComponent(e.feed_id)}/${encodeURIComponent(e.guid)}`;
   try{
     if(a==='play') play(e, encId!=null ? enc : undefined);
+    if(a==='share') await share(e.title||'', encId!=null ? enc.url : e.link, el);
     if(a==='flag'){ e.flagged=!e.flagged; await api(path+'/flags',{method:'POST',body:JSON.stringify({flagged:e.flagged})}); redraw(); }
     if(a==='read'){ await setRead(e,!e.read); redraw(); }
     if(a==='get'){