fix: allow dots in usernames; BCrypt fallback in password verifier for v1 migrations

crates/adapters/auth/Cargo.toml

@@ -13,4 +13,5 @@ tokio        = { workspace = true }
 serde        = { workspace = true }
 jsonwebtoken = "9"
 argon2       = "0.5"
+bcrypt        = "0.15"
 rand          = "0.8"

crates/adapters/auth/src/lib.rs

@@ -76,6 +76,10 @@ impl PasswordHasher for Argon2PasswordHasher {
     }
 
     async fn verify(&self, plain: &str, hash: &PasswordHash) -> Result<bool, DomainError> {
+        if hash.0.starts_with("$2") {
+            return bcrypt::verify(plain, &hash.0)
+                .map_err(|e| DomainError::Internal(e.to_string()));
+        }
         use argon2::{password_hash::PasswordHash as ArgonHash, Argon2, PasswordVerifier};
         let parsed = ArgonHash::new(&hash.0).map_err(|e| DomainError::Internal(e.to_string()))?;
         Ok(Argon2::default()

crates/domain/src/value_objects.rs

@@ -44,9 +44,12 @@ impl Username {
         if s.is_empty() || s.len() > 32 {
             return Err(DomainError::InvalidInput("username: 1-32 chars".into()));
         }
-        if !s.chars().all(|c| c.is_alphanumeric() || c == '_') {
+        if !s
+            .chars()
+            .all(|c| c.is_alphanumeric() || c == '_' || c == '.')
+        {
             return Err(DomainError::InvalidInput(
-                "username: alphanumeric or underscore only".into(),
+                "username: alphanumeric, underscore, or dot only".into(),
             ));
         }
         Ok(Self(s))