fix: show Share button for document owner by suppressing ownerDID in view template

internal/handler/handler.go

···
 }
 
 // documentView is the shared implementation for viewing a document given an ownerDID and rkey.
-func (h *Handler) documentView(w http.ResponseWriter, r *http.Request, ownerUserID, ownerDID, rkey string) {
+// isOwner should be true when the current user owns the document; it suppresses the ownerDID
+// in the template so the edit button links to /docs/{rkey}/edit rather than the collaborator URL.
+func (h *Handler) documentView(w http.ResponseWriter, r *http.Request, ownerUserID, ownerDID, rkey string, isOwner bool) {
 	client, err := h.xrpcClient(ownerUserID)
 	if err != nil {
 		http.Error(w, "Could not connect to PDS", 500)
···
 		Rendered template.HTML
 		OwnerDID string // non-empty when viewing a collaborator's document
 	}
+	// Only set OwnerDID when the viewer is not the owner; the template uses
+	// a non-empty OwnerDID to generate the collaborator edit URL.
+	templateOwnerDID := ownerDID
+	if isOwner {
+		templateOwnerDID = ""
+	}
 	h.render(w, "document_view.html", PageData{
 		Title:   doc.Title,
 		User:    user,
-		Content: DocumentViewData{Doc: doc, Rendered: template.HTML(rendered), OwnerDID: ownerDID},
+		Content: DocumentViewData{Doc: doc, Rendered: template.HTML(rendered), OwnerDID: templateOwnerDID},
 	})
 }
 
···
 		http.Error(w, "Could not connect to PDS", 500)
 		return
 	}
-
-	h.documentView(w, r, user.ID, client.DID(), rkey)
+	h.documentView(w, r, user.ID, client.DID(), rkey, true)
 }
 
 // CollaboratorDocumentView renders a document owned by another user (collaborator access).
···
 		return
 	}
 
-	h.documentView(w, r, ownerUser.ID, ownerDID, rkey)
+	h.documentView(w, r, ownerUser.ID, ownerDID, rkey, false)
 }
 
 // documentEdit is the shared implementation for the edit page.