feat: auth hardening + codebase quality sweep

Refresh tokens: RefreshToken entity, PostgresRefreshTokenRepository,
login returns refresh token, POST /auth/refresh (rotation), POST /auth/logout,
JWT expiry 24h→1h, configurable via with_expiry().

Route protection: require_auth middleware on protected routes,
public routes split (register, login, refresh, sharing/access).

Authorization: caller_id added to ReadAssetFileQuery, ReadDerivativeQuery,
GetStackQuery, DeleteStackCommand with ownership checks. Admin-only gates
on processing, storage, sidecar, duplicates handlers.

Quality fixes: visibility filtering bypass in search(), unwrap panics in
date parsing, DRY auth header parsing, centralized parsers module,
email validation via email_address crate, value objects (Username, MimeType,
RelativePath), domain events (UserCreated, UserDeleted, AlbumCreated,
TagCreated, DuplicateDetected), postgres error mapping for constraint
violations, OptionExt::or_not_found helper, in_memory_repo! macro,
GetStackQuery moved to queries, album add_entry 200→201.

crates/domain/src/identity/entities.rs

@@ -1,5 +1,5 @@
 use crate::common::errors::DomainError;
-use crate::common::value_objects::{Email, PasswordHash, SystemId};
+use crate::common::value_objects::{DateTimeStamp, Email, PasswordHash, SystemId};
 use chrono::{DateTime, Utc};
 use std::collections::HashSet;
 
@@ -141,6 +141,35 @@ impl User {
     }
 }
 
+// --- RefreshToken ---
+
+#[derive(Debug, Clone)]
+pub struct RefreshToken {
+    pub token_id: SystemId,
+    pub user_id: SystemId,
+    pub token_hash: String,
+    pub expires_at: DateTimeStamp,
+    pub revoked: bool,
+    pub created_at: DateTimeStamp,
+}
+
+impl RefreshToken {
+    pub fn new(user_id: SystemId, token_hash: String, expires_at: DateTimeStamp) -> Self {
+        Self {
+            token_id: SystemId::new(),
+            user_id,
+            token_hash,
+            expires_at,
+            revoked: false,
+            created_at: DateTimeStamp::now(),
+        }
+    }
+
+    pub fn is_valid(&self) -> bool {
+        !self.revoked && *self.expires_at.as_datetime() > Utc::now()
+    }
+}
+
 // --- Group ---
 
 #[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]