Add password change functionality

- Add POST /api/auth/password API endpoint
  - Requires authentication and current password verification
  - Invalidates all other sessions after password change
  - Keeps current session active

- Add window.changePassword() console function
  - Matches existing login flow pattern
  - Usage: changePassword("current", "new")

- Add 'lookbook set-password' CLI command
  - Interactive password reset (no current password required)
  - Useful for recovery scenarios
  - Invalidates all sessions

- Add session.QDeleteAllExcept() and session.QDeleteAll()
  - Support for invalidating sessions after password change

internal/static/js/app.js

@@ -36,6 +36,28 @@ window.logout = async () => {
   }
 };
 
+window.changePassword = async (currentPassword, newPassword) => {
+  if (!currentPassword || !newPassword) {
+    console.error('Usage: changePassword("current-password", "new-password")');
+    return;
+  }
+  try {
+    const res = await fetch("/api/auth/password", {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify({ currentPassword, newPassword }),
+    });
+    const data = await res.json();
+    if (res.ok) {
+      console.log("Password changed successfully!");
+    } else {
+      console.error(data.error || "Failed to change password");
+    }
+  } catch (err) {
+    console.error("Password change error:", err);
+  }
+};
+
 // Modal functions
 function showAddModal() {
   document.getElementById("add-modal").classList.add("active");