feat: vendor and censor the phishing blocklist at build time (closes #219)

The blocklist URL in shipped code named a competitor and pointed at a moving
ref, and the extension re-fetched from it every 24 hours, which also meant a
third party decided what this wallet warns about. All of that is gone.

script/vendor-blocklist fetches upstream at a pinned commit, verifies the
sha256 of the bytes that commit serves, and writes
src/shared/phishingBlocklist.json. It is build-time tooling, never shipped, and
the one place in the repo that names the upstream project; a source reference
nobody can verify is not a source reference.

The artifact stores truncated sha256 digests rather than domain names. That is
what censors it: the previous file contained the competitor's name 6,475 times,
as phishing domains impersonating them, and not one of those domains is
dropped. It also makes lookups a binary search over a fixed-width string, so
nothing is built at module load — which matters on MV3, where the worker
re-evaluates the module on every wake — and takes the file from 8.7 MB to
1.7 MB.

script/check-censored enforces the rest: it reads the name out of the vendoring
script rather than repeating it, and fails on any occurrence in the working
tree or under dist/ that is not one of the two literals shipped code cannot
avoid. It runs in make check, which inspects dist/ when there is one and says
loudly when there is not, and again with --require-dist at the end of every
make build.

Removing the runtime fetch retires the delta, the extension-storage persistence
and the 24-hour alarm from #158. A retired alarm is now cleared rather than
left waking the worker forever on installs that already have it.

The e2e suite drives the warning end to end from a real blocklisted origin
served as a real http(s) site, with a control asserting the banner stays hidden
for one that is not listed. Its service-worker interception canary needed a new
anchor, since the startup fetch it used to watch for no longer happens: it now
wakes the worker with a message and asks it for one throwaway fetch.

LICENSE no longer cites a repository that returns 404.

eslint.config.js gains one block: script/lib/ holds node programs the shell
entrypoints call, and without it they lint with no globals at all.

src/background/index.js

@@ -27,14 +27,9 @@ const {
     TX_STAGE_NONCE,
 } = require("../shared/approvalVerify");
 const { prepareApprovalTx } = require("../shared/approvalTx");
-const {
-    isPhishingDomain,
-    refreshPhishingListOnSchedule,
-    initPhishingList,
-} = require("../shared/phishingDomains");
+const { isPhishingDomain } = require("../shared/phishingDomains");
 const {
     BALANCE_REFRESH_ALARM,
-    PHISHING_REFRESH_ALARM,
     BALANCE_REFRESH_PERIOD_MINUTES,
     ensureRecurringAlarms,
     registerAlarmHandlers,
@@ -1013,26 +1008,20 @@ async function backgroundRefresh() {
     await saveState();
 }
 
-// Both recurring jobs run off alarms, not timers. On Chrome MV3 this file is
+// The recurring job runs off an alarm, not a timer. On Chrome MV3 this file is
 // a service worker that the browser terminates after about 30 seconds idle,
 // so a setInterval would only ever survive until the first idle period and
 // module-level state does not outlive it. Alarms are held by the browser and
 // wake the worker to deliver them.
 registerAlarmHandlers({
     [BALANCE_REFRESH_ALARM]: backgroundRefresh,
-    // The scheduled refresh, which restores persisted state on a freshly
-    // revived worker and then fetches unconditionally. The freshness guards
-    // belong to the startup path; applying them here would make the tick skip
-    // itself.
-    [PHISHING_REFRESH_ALARM]: refreshPhishingListOnSchedule,
 });
 
 // Everything the background context needs re-established on start. This runs
 // on a fresh install, on browser startup, and on every revival of a
 // terminated worker, so it must be idempotent: ensureRecurringAlarms() only
-// creates alarms that are missing or carrying a stale period, and
-// initPhishingList() fetches only when the persisted timestamps say the list
-// is stale.
+// creates alarms that are missing or carrying a stale period, and only clears
+// retired ones that are still registered.
 //
 // On a fresh install the top-level call and the onInstalled listener both run,
 // close enough together that both could see an alarm missing and create it.
@@ -1043,10 +1032,7 @@ let backgroundJobsRun = null;
 
 function startBackgroundJobs() {
     if (backgroundJobsRun) return backgroundJobsRun;
-    backgroundJobsRun = Promise.all([
-        ensureRecurringAlarms(),
-        initPhishingList(),
-    ])
+    backgroundJobsRun = ensureRecurringAlarms()
         .catch((err) => {
             // An alarm that failed to schedule means a recurring job silently
             // never runs again; it must not be an unhandled rejection.