Scaffold workspace, shared types and requirements spec

Cargo workspace with core/ble/fit/probe crates. crates/core/src/types.rs
is the fixed contract between the BLE layer, ride engine and UI.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src-tauri/capabilities/default.json

@@ -0,0 +1,14 @@
+{
+  "$schema": "../gen/schemas/desktop-schema.json",
+  "identifier": "default",
+  "description": "Permissions for the BikeControl main window.",
+  "windows": ["main"],
+  "permissions": [
+    "core:default",
+    "core:event:default",
+    "core:window:default",
+    "core:webview:default",
+    "core:app:default",
+    "dialog:default"
+  ]
+}