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/app/state/plaintextCaches.ts

@@ -139,6 +139,31 @@ const clearAccountScopedFlags = (userId?: string): void => {
   });
 };
 
+/**
+ * [Gitea #266] Remembered widget approvals (`lotus.widgetConsent.<room>.<widget>`,
+ * widgetUtils.ts) would otherwise apply silently to the next account on this
+ * device, and their keys list the previous account's rooms. Kept as a string
+ * here so logout doesn't pull the widget code into the entry chunk; a test
+ * checks it matches WIDGET_CONSENT_PREFIX.
+ */
+export const WIDGET_CONSENT_KEY_PREFIX = 'lotus.widgetConsent.';
+const clearWidgetConsents = (): void => {
+  let keys: string[];
+  try {
+    keys = Object.keys(localStorage);
+  } catch {
+    return;
+  }
+  keys.forEach((key) => {
+    if (!key.startsWith(WIDGET_CONSENT_KEY_PREFIX)) return;
+    try {
+      localStorage.removeItem(key);
+    } catch {
+      // best-effort
+    }
+  });
+};
+
 export const clearPlaintextCaches = (userId?: string): void => {
   wiped = true;
   clearTranslationCache();
@@ -153,5 +178,6 @@ export const clearPlaintextCaches = (userId?: string): void => {
   clearStatusMessage();
   clearCallVolumesAndSyncMeta(userId);
   clearAccountScopedFlags(userId);
+  clearWidgetConsents();
   if (userId) clearNavToActivePathStore(userId);
 };