Add Foundry mobile layout with Tauri iOS/Android support

- Add responsive mobile layout with bottom pill tab bar, swipe navigation, and task list as home screen
- Add platform detection (useIsMobile hook) with viewport breakpoint and VITE_MOBILE build flag
- Mobile-optimize settings/billing/account pages (single-column layout with horizontal tabs)
- Add iOS safe area inset handling with 47px minimum padding
- Scaffold Tauri v2 mobile targets (iOS/Android) with platform-gated sidecar and capabilities
- Add notification sound support and mobile build script

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

foundry/packages/desktop/src-tauri/gen/schemas/capabilities.json

@@ -1 +1,24 @@
-{"default":{"identifier":"default","description":"Default capability for Foundry desktop","local":true,"windows":["main"],"permissions":["core:default","core:window:allow-start-dragging","shell:allow-open",{"identifier":"shell:allow-execute","allow":[{"args":true,"name":"sidecars/foundry-backend","sidecar":true}]},{"identifier":"shell:allow-spawn","allow":[{"args":true,"name":"sidecars/foundry-backend","sidecar":true}]}]}}
+{
+  "default": {
+    "identifier": "default",
+    "description": "Default capability for Foundry desktop",
+    "local": true,
+    "windows": ["main"],
+    "permissions": [
+      "core:default",
+      "core:window:allow-start-dragging",
+      "shell:allow-open",
+      { "identifier": "shell:allow-execute", "allow": [{ "args": true, "name": "sidecars/foundry-backend", "sidecar": true }] },
+      { "identifier": "shell:allow-spawn", "allow": [{ "args": true, "name": "sidecars/foundry-backend", "sidecar": true }] }
+    ],
+    "platforms": ["macOS", "windows", "linux"]
+  },
+  "mobile": {
+    "identifier": "mobile",
+    "description": "Capability for Foundry mobile (iOS/Android)",
+    "local": true,
+    "windows": ["main"],
+    "permissions": ["core:default"],
+    "platforms": ["iOS", "android"]
+  }
+}