fix(app): passphrase dialog — remove CSP meta, check crypto.subtle availability

- Remove CSP meta tag from index.html (breaks Vite HMR, should be
  set via HTTP headers in production nginx instead)
- isCryptoEnabled() now checks crypto.subtle is available (undefined
  over HTTP on non-localhost origins)
- Add try/catch + error feedback to passphrase submit flow
- PassphraseDialog accepts error prop, focuses input on visible

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/app/src/components/ui/PassphraseDialog.vue

@@ -54,8 +54,8 @@
             @keydown.enter="handleSubmit"
           />
 
-          <p v-if="errorMessage" class="text-xs text-red-400 px-1">
-            {{ errorMessage }}
+          <p v-if="errorMessage || props.error" class="text-xs text-red-400 px-1">
+            {{ errorMessage || props.error }}
           </p>
         </div>
 
@@ -86,11 +86,12 @@
 </template>
 
 <script setup lang="ts">
-import { ref, computed, onMounted, nextTick } from 'vue'
+import { ref, computed, watch, nextTick } from 'vue'
 
 const props = defineProps<{
   visible: boolean
   isCreating: boolean
+  error?: string
 }>()
 
 const emit = defineEmits<{
@@ -124,7 +125,7 @@ function handleSkip() {
   emit('skip')
 }
 
-onMounted(() => {
-  nextTick(() => inputRef.value?.focus())
-})
+watch(() => props.visible, (v) => {
+  if (v) nextTick(() => inputRef.value?.focus())
+}, { immediate: true })
 </script>