Remove ?token= deletion-token path (#143)

The deletion token was accepted via the ?token= query parameter on both
DELETE /api/pastes/{id} and /redeem, and round-tripped through the paste
URL after creation. URL-carried bearer secrets leak into reverse-proxy
access logs and browser history.

- API: deletion tokens are now accepted only via the Authorization header
  (Bearer/Token/bare); query params are ignored on both endpoints
- Web create flow: token moves to the browser via a short-lived tok_<id>
  HttpOnly cookie instead of the redirect URL; the paste view reads it
  from the cookie, never from ?token=
- Web view: the delete button calls redeem() which takes the token from
  sessionStorage and sends it as an Authorization header
- Tests: correct token in query must be rejected (403/400); header path
  still deletes/redeems; extraction unit cases updated

Fixes #143

internal/web/templates/new.html

@@ -291,7 +291,9 @@ function finishCreate(data) {
       setTimeout(() => { copyBtn.classList.remove('ok'); copyBtn.textContent = '⧉'; }, 2000);
     } catch(e) { toast('Copy failed', 'error'); }
   });
-  const dest = '/' + data.id + '?created=1&token=' + encodeURIComponent(data.deletion_token || '');
+  // token carried via sessionStorage, never in the URL (#143)
+  const dest = '/' + data.id + '?created=1';
+  try { sessionStorage.setItem('deletion_token_' + data.id, data.deletion_token || ''); } catch(e) {}
   // password-protected: unlock now with the password we already have (#26)
   if ($('haspw').checked && data.id) {
     const fd = new FormData();

internal/web/templates/paste.html

@@ -9,7 +9,7 @@
       <button type="button" class="iconbtn wrap-toggle" title="Toggle line wrap" aria-pressed="false">wrap</button>
       <a class="iconbtn" href="/raw/{{.ID}}">raw</a>
       <a class="iconbtn" href="#" id="copy-btn" onclick="copyContent(this); return false;">copy</a>
-      {{if .DeletionToken}}<a class="iconbtn danger" href="#" onclick="redeem('{{.DeletionToken}}'); return false;">delete</a>{{end}}
+      {{if .DeletionToken}}<a class="iconbtn danger" href="#" onclick="redeem(); return false;">delete</a>{{end}}
     </div>
   </div>
   <div class="float">
@@ -89,9 +89,12 @@ function copyContent(btn) {
     toast('Copied', 'success');
   }
 }
-function redeem(token) {
+function redeem() {
   if (!confirm('Hard delete this paste immediately?')) return;
-  fetch('/api/pastes/{{.ID}}/redeem?token=' + encodeURIComponent(token), {method: 'DELETE'})
+  let tok = '';
+  try { tok = sessionStorage.getItem('deletion_token_{{.ID}}') || ''; } catch(e) {}
+  if (!tok) { alert('deletion token not available in this browser'); return; }
+  fetch('/api/pastes/{{.ID}}/redeem', {method: 'DELETE', headers: {'Authorization': 'Bearer ' + tok}})
     .then(r => { if (r.ok) location.href = '/history'; else alert('delete failed'); });
 }
 </script>

internal/web/web.go

@@ -310,7 +310,13 @@ func (h *Handlers) HandlePasteView(w http.ResponseWriter, r *http.Request) {
 	}
 
 	justCreated := r.URL.Query().Get("created") == "1"
-	token := r.URL.Query().Get("token")
+	// #143: the deletion token is no longer round-tripped through the URL
+	// (?token= leaks into access logs and history). The create flow sets a
+	// short-lived tok_<id> cookie; the paste view reads it once from there.
+	token := ""
+	if c, err := r.Cookie("tok_" + row.ID); err == nil {
+		token = c.Value
+	}
 	if justCreated && token != "" {
 		// one-time display of the deletion token via the created banner
 		http.SetCookie(w, &http.Cookie{Name: "tok_" + row.ID, Value: token, Path: "/", MaxAge: 60, HttpOnly: true, SameSite: http.SameSiteLaxMode})