Fix race condition in handleCreateGroup state management

[Copilot]

State was being set before database operations completed in handleCreateGroup. If writes failed, users would see the map view without actually being group members.

Changes

• Moved state updates (setCurrentGroup, setGroupCode, setCurrentGroupName) to execute after database operations complete
• State is now only set if both critical writes succeed: group metadata and member addition

Before

setCurrentGroup(finalCode);  // State set early
await database.ref(`groups/${finalCode}/meta`).set({...});
await database.ref(`groups/${finalCode}/members/${user.uid}`).set({...});
// If these fail, user sees map view but isn't in group

After

await database.ref(`groups/${finalCode}/meta`).set({...});
await database.ref(`groups/${finalCode}/members/${user.uid}`).set({...});
// Only set state after critical operations succeed
setCurrentGroup(finalCode);

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