fix(security): widget consents and shared files cleared on logout; forged shares refused (#266, #267)

#266: remembered widget approvals (lotus.widgetConsent.*) survived logout,
so they applied silently to the next account on the device and listed the
previous account's rooms; clearPlaintextCaches now sweeps them. Space
structure, call membership and Lotus room-policy state join
PROTECTED_STATE_TYPES, so no widget can be granted them.

#267: any website could auto-submit a form to /share-target and land the
user in the share picker with attacker-chosen text and files. The worker
now refuses a share whose Origin is another site. (Sec-Fetch-Site, as the
issue suggested, never reaches a service worker: checked in Chromium.)
Origin null/absent, as the OS share sheet sends, stays accepted, and
/share now says the content came from another app or website. Both logout
paths await clearSharedPayload(); the server-forced one also clears the
soundboard clip cache, as #57 intended.

Fixes #266
Fixes #267

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5

src/sw.ts

@@ -1,7 +1,7 @@
 /// <reference lib="WebWorker" />
 
 import { precacheAndRoute, type PrecacheEntry } from 'workbox-precaching';
-import { SHARE_TARGET_PATH, stashSharedForm } from './swShare';
+import { isTrustedShareRequest, SHARE_TARGET_PATH, stashSharedForm } from './swShare';
 import { pickReplySession, replyFailureText, sendNotificationReply } from './swReply';
 
 export type {};
@@ -249,6 +249,11 @@ self.addEventListener('fetch', (event: FetchEvent) => {
   // share_target). Stash the form and bounce to the in-app /share page.
   if (method === 'POST' && new URL(url).pathname.endsWith(SHARE_TARGET_PATH)) {
     const base = new URL(url).pathname.slice(0, -SHARE_TARGET_PATH.length);
+    // [Gitea #267] A cross-site form posting here is not a share: drop it.
+    if (!isTrustedShareRequest(event.request.headers, self.location.origin)) {
+      event.respondWith(Response.redirect(`${base}/`, 303));
+      return;
+    }
     event.respondWith(
       stashSharedForm(event.request, base).catch(() => Response.redirect(`${base}/`, 303)),
     );