Replace .log w/ explicit .debug/.error functions

This would make the intention more explicit so we can overload different logging types as well like keychain, security events, etc…

Search/Replace Strategies:

1.
Search regex: `SecureLogger\.log\(\s*(.*?),\s*category:\s*(.*?),\s*level:\s*\.(\w+)\s*\)`
Replace regex: `SecureLogger.$3($1, category: $2)`

Sample input:
```
SecureLogger.log(
    "🔄 Found favorite for '\(peerInfo.nickname)' by nickname, updating noise key",
    category: .session,
    level: .debug
)
```

Sample output:
`SecureLogger.debug("🔄 Found favorite for '\(peerInfo.nickname)' by nickname, updating noise key", category: .session)`

---

2.
Search regex: `SecureLogger\.log\((.*?)\)`
Replace regex: `SecureLogger.debug($1)` (as it’s the default level)

Sample input:
`SecureLogger.log("some text")`

Sample output:
`SecureLogger.debug("some text")`

---

3
Manual changes:
ChatViewModel line 5393 (commented code)
NostrRelayManager line 196 (commented code)
NostrRelayManager lines 346-350 (if/else logic)
NostrRelayManager line 371 (commented code)

bitchat/Services/PrivateChatManager.swift

@@ -228,8 +228,7 @@ final class PrivateChatManager: ObservableObject {
         
         // Route via MessageRouter to avoid handshakeRequired spam when session isn't established
         if let router = messageRouter {
-            SecureLogger.log("PrivateChatManager: sending READ ack for \(message.id.prefix(8))… to \(senderPeerID.prefix(8))… via router",
-                            category: .session, level: .debug)
+            SecureLogger.debug("PrivateChatManager: sending READ ack for \(message.id.prefix(8))… to \(senderPeerID.prefix(8))… via router", category: .session)
             Task { @MainActor in
                 router.sendReadReceipt(receipt, to: senderPeerID)
             }