feat(gui): profile switcher chip in header

Visible visual indicator of the active profile + click-to-swap dropdown.
Closes the last small UX gap pointed out in earlier sessions.

Tauri (crates/jarvis-gui/src/tauri_commands/profile.rs)
  - profile_list()   → Vec<String> of available profile names
  - profile_active() → {name, description, icon, greeting}
  - profile_set(name) → swaps active profile, returns new active

Frontend (frontend/src/components/Header.svelte)
  - Polls profile_active every 5 seconds.
  - Shows a coloured chip with icon+name when profile != "default"
    (orange tint, attention-grabbing). For "default" — muted star chip.
  - Click opens a dropdown listing all profile names; click one → swap.
  - Dropdown closes on outside-click (shared handler with lang dropdown).
  - SCSS styled to match existing aesthetic.

Build: cargo build --release -p jarvis-gui green (2m).

Now the user can see at a glance which profile is active (e.g. "💼 work")
without having to ask voice or open Settings.

crates/jarvis-gui/src/tauri_commands/profile.rs

@@ -0,0 +1,38 @@
+//! Tauri commands for profile switching.
+
+use serde::Serialize;
+
+#[derive(Serialize)]
+pub struct ProfileInfo {
+    pub name: String,
+    pub description: String,
+    pub icon: String,
+    pub greeting: String,
+}
+
+#[tauri::command]
+pub fn profile_list() -> Vec<String> {
+    jarvis_core::profiles::list()
+}
+
+#[tauri::command]
+pub fn profile_active() -> ProfileInfo {
+    let p = jarvis_core::profiles::active();
+    ProfileInfo {
+        name: p.name,
+        description: p.description,
+        icon: p.icon,
+        greeting: p.greeting,
+    }
+}
+
+#[tauri::command]
+pub fn profile_set(name: String) -> Result<ProfileInfo, String> {
+    let p = jarvis_core::profiles::set_active(&name)?;
+    Ok(ProfileInfo {
+        name: p.name,
+        description: p.description,
+        icon: p.icon,
+        greeting: p.greeting,
+    })
+}