test(e2e): Playwright UI smoke + Go integration tests against MAS

- Playwright e2e against Vite dev server (LoginScreen renders, homeserver
  visible, version pinned). Fallback documented to swap to `wails dev
  -browser` via WAILS_DEV_URL when full backend bindings are required.
- Go integration tests (//go:build integration,goolm) for Start +
  ListRooms + LoadTimeline + SendText + GetDiagnostics against real
  Synapse. Skip cleanly if MATRIX_INTEGRATION_TOKEN/USER env vars unset
  so CI never breaks unattended.
- pnpm e2e/e2e:ui/e2e:report scripts. Per-run keyring namespace +
  t.TempDir XDG_CONFIG_HOME so integration tests don't clobber the
  production keyring entry.

E2E.md explains how to run each layer + limits (OIDC not automated).

frontend/pnpm-lock.yaml

@@ -27,6 +27,9 @@ importers:
         specifier: ^18.3.1
         version: 18.3.1(react@18.3.1)
     devDependencies:
+      '@playwright/test':
+        specifier: ^1.60.0
+        version: 1.60.0
       '@testing-library/jest-dom':
         specifier: ^6.9.1
         version: 6.9.1
@@ -417,6 +420,11 @@ packages:
     peerDependencies:
       react: ^18.x || ^19.x
 
+  '@playwright/test@1.60.0':
+    resolution: {integrity: sha512-O71yZIbAh/PxDMNGns37GHBIfrVkEVyn+AXyIa5dOTfb4/xNvRWV+Vv/NMbNCtODB/pO7vLlF2OTmMVLhmr7Ag==}
+    engines: {node: '>=18'}
+    hasBin: true
+
   '@polka/url@1.0.0-next.29':
     resolution: {integrity: sha512-wwQAWhWSuHaag8c4q/KN/vCoeOJYshAIvMQwD4GpSb3OiZklFfvAgmj0VCBBImRpuF/aFgIRzllXlVX93Jevww==}
 
@@ -795,6 +803,11 @@ packages:
   flatted@3.4.2:
     resolution: {integrity: sha512-PjDse7RzhcPkIJwy5t7KPWQSZ9cAbzQXcafsetQoD7sOJRQlGikNbx7yZp2OotDnJyrDcbyRq3Ttb18iYOqkxA==}
 
+  fsevents@2.3.2:
+    resolution: {integrity: sha512-xiqMQR4xAeHTuB9uWm+fFRcIOgKBMiOBP+eXiyT7jsgVCq1bkVygt00oASowB7EdtpOHaaPgKt812P9ab+DDKA==}
+    engines: {node: ^8.16.0 || ^10.6.0 || >=11.0.0}
+    os: [darwin]
+
   fsevents@2.3.3:
     resolution: {integrity: sha512-5xoDfX+fL7faATnagmWPpbFtwh/R77WmMMqqHGS65C3vvB0YHrgF+B1YmZ3441tMj5n63k0212XNoJwzlhffQw==}
     engines: {node: ^8.16.0 || ^10.6.0 || >=11.0.0}
@@ -906,6 +919,16 @@ packages:
     resolution: {integrity: sha512-QP88BAKvMam/3NxH6vj2o21R6MjxZUAd6nlwAS/pnGvN9IVLocLHxGYIzFhg6fUQ+5th6P4dv4eW9jX3DSIj7A==}
     engines: {node: '>=12'}
 
+  playwright-core@1.60.0:
+    resolution: {integrity: sha512-9bW6zvX/m0lEbgTKJ6YppOKx8H3VOPBMOCFh2irXFOT4BbHgrx5hPjwJYLT40Lu+4qtD36qKc/Hn56StUW57IA==}
+    engines: {node: '>=18'}
+    hasBin: true
+
+  playwright@1.60.0:
+    resolution: {integrity: sha512-hheHdokM8cdqCb0lcE3s+zT4t4W+vvjpGxsZlDnikarzx8tSzMebh3UiFtgqwFwnTnjYQcsyMF8ei2mCO/tpeA==}
+    engines: {node: '>=18'}
+    hasBin: true
+
   postcss@8.5.15:
     resolution: {integrity: sha512-FfR8sjd4em2T6fb3I2MwAJU7HWVMr9zba+enmQeeWFfCbm+UOC/0X4DS8XtpUTMwWMGbjKYP7xjfNekzyGmB3A==}
     engines: {node: ^10 || ^12 || >=14}
@@ -1553,6 +1576,10 @@ snapshots:
     dependencies:
       react: 18.3.1
 
+  '@playwright/test@1.60.0':
+    dependencies:
+      playwright: 1.60.0
+
   '@polka/url@1.0.0-next.29': {}
 
   '@rolldown/pluginutils@1.0.0-beta.27': {}
@@ -1901,6 +1928,9 @@ snapshots:
 
   flatted@3.4.2: {}
 
+  fsevents@2.3.2:
+    optional: true
+
   fsevents@2.3.3:
     optional: true
 
@@ -1994,6 +2024,14 @@ snapshots:
 
   picomatch@4.0.4: {}
 
+  playwright-core@1.60.0: {}
+
+  playwright@1.60.0:
+    dependencies:
+      playwright-core: 1.60.0
+    optionalDependencies:
+      fsevents: 2.3.2
+
   postcss@8.5.15:
     dependencies:
       nanoid: 3.3.12