NPC editor, NPC tokens from library, admin management

- NPC library (own + shared) built on the character wizard with a free NPC preset
- NPC tokens in map editor and lobby, DM sheet on token click, DM checks for NPCs
- Admins can promote/demote other users

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HJhXuLD2Z6hv3Wqeq9UL9K

frontend/src/PaperSheet.jsx

@@ -158,6 +158,13 @@ export default function PaperSheet({ data, baseRules, tools, bare, onRoll }) {
               ))}
             </div>
           </div>
+          {data.npc && (data.abilities || data.loot || data.background) && (
+            <div className="psec pnpc">
+              {data.background && <><h3>Description</h3><p className="pre">{data.background}</p></>}
+              {data.abilities && <><h3>Abilities and attacks</h3><p className="pre">{data.abilities}</p></>}
+              {data.loot && <><h3>Loot</h3><p className="pre">{data.loot}</p></>}
+            </div>
+          )}
           <div className="psec pnotes"><h3>Conditions &amp; notes</h3><div className="plines" /></div>
           <Foot n={1} />
         </section>