feat(core): add password hashing and token generation interfaces

src/FiscalOS.Core/Authentication/IPasswordHasher.cs

@@ -0,0 +1,7 @@
+namespace FiscalOS.Core.Authentication;
+
+public interface IPasswordHasher
+{
+  string Hash(string password);
+  bool Verify(string providedPassword, string hashedPassword);
+}

src/FiscalOS.Core/Authentication/ITokenGenerator.cs

@@ -0,0 +1,7 @@
+namespace FiscalOS.Core.Authentication;
+
+public interface ITokenGenerator
+{
+  string GenerateAccessToken(User user);
+  RefreshToken GenerateRefreshToken(User user);
+}