BUG: Provider map race condition in main model

[andrinoff]

Describe the bug
Provider map at main.go:130-145 accessed without locking in getProvider() while other goroutines modify in initProviders(). Classic race condition.

To reproduce

1. Build with -race flag
2. Run matcha with multiple accounts
3. Race detector reports concurrent map access

Expected behavior
Use sync.RWMutex to protect provider map access

Matcha version
master

OS
All

Additional context
File: main.go lines 130-145
Concurrent map access without sync

[mavonx]

/assign