ci: run the checks that only ran on a laptop; mobile in CI; retries 0

CI ran Playwright (chromium-desktop) + the dependency audit and nothing else. cargo test,
clippy, the frontend vitest suite, svelte-check and the e2e typecheck were all green on a
developer's machine and gated NOTHING.

  checks.yml (new): cargo test (with a Postgres service; --test-threads bounded so the
    sqlx per-test DBs can't exhaust connections) + clippy; vitest + svelte-check; e2e tsc.
  e2e.yml: also run the chromium-mobile project — 22 tests (focus traps, touch targets,
    safe-area, viewport reflow) that never ran in CI on a phone-first app.
  playwright.config: widen webkit-iphone beyond @smoke (2 specs) to the core guest journeys
    (auth/upload/feed) — iOS Safari is the PRIMARY browser here; and retries 2 → 0.

retries:0 is deliberate and against the usual advice: this repo's real bugs are races, a
race is indistinguishable from a flake from outside, and a retry resolves that ambiguity
toward "flake" every time — it took a real 3%-flaky product bug from 1-in-33 to 1-in-37000,
green. A flake here is a bug report.

Not gated: cargo fmt (the tree has never been rustfmt'd — a 112-file reformat would bury
every real diff; do it separately). WebKit widening is unverified locally (needs libavif16
via sudo), so its first CI run may surface real iOS bugs.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

e2e/playwright.config.ts

@@ -23,7 +23,25 @@ export default defineConfig({
   outputDir: './test-results',
   fullyParallel: false,            // Single shared backend → tests TRUNCATE between, so don't run in parallel.
   forbidOnly: !!process.env.CI,
-  retries: process.env.CI ? 2 : 0,
+  // NO RETRIES — not even in CI. This is deliberate and it is the opposite of the usual advice.
+  //
+  // The standard case for retries is "the environment is flaky, the product isn't." That argument
+  // does not hold here. This backend's real bugs ARE races (the last several fixes were all export
+  // concurrency), and from the outside a race is indistinguishable from a flake — so a retry
+  // resolves that ambiguity, silently, in favour of "flake", every single time.
+  //
+  // The numbers make it concrete. A test that fails 3% of runs reports a bug roughly 1 run in 33.
+  // Under `retries: 2` it fails the build only when it fails three times in a row: ~1 in 37,000.
+  // We had exactly such a test, and it was reporting a REAL user-facing bug (a suggestion button
+  // that committed on mousedown and destroyed itself mid-click). Retries would have buried it
+  // forever, and buried it GREEN, so nobody would even have seen an amber.
+  //
+  // Worse, a retry does not re-run the failing conditions — it runs a CLEANER environment (the
+  // interfering background worker from the previous test has since finished). So the mechanism is
+  // specifically good at hiding exactly the cross-test contamination this suite is prone to.
+  //
+  // A flake here is a bug report. Treat it as one.
+  retries: 0,
   workers: 1,                      // One worker. Multi-worker needs per-worker isolated DBs (Phase 2+).
   reporter: [
     ['list'],
@@ -127,7 +145,12 @@ export default defineConfig({
     {
       name: 'webkit-iphone',
       use: { ...devices['iPhone 14 Pro'] },
-      grep: /@smoke/,
+      // The PRIMARY user of this app is a wedding guest opening a QR link in iOS Safari. Gating
+      // that on `@smoke` — which exists on exactly two specs — meant the entire iOS guarantee was
+      // one happy path and one join test. Every other UA here is a secondary browser and a smoke
+      // check is proportionate; WebKit is not. Give it the core journeys the guest actually walks:
+      // join/recover, upload, and browse the feed.
+      testMatch: ['**/__smoke/**', '**/01-auth/**', '**/02-upload/**', '**/03-feed/**'],
     },
     {
       name: 'firefox-android',