perf: migrate all user/session/auth IDs from VARCHAR(36) to native UUID

- Schema: all ~15 VARCHAR(36) columns → UUID with DEFAULT gen_random_uuid()
- Domain entities: User, Session, DeviceCode, AppPassword, Share → id: Uuid
- DTOs: CurrentUser.id → Uuid (API boundary DTOs keep String for JSON)
- Auth middleware: parse JWT claims.sub (String) → Uuid at boundary
- All repository traits, port traits, service impls updated end-to-end
- Handlers: pass Uuid by value (Copy, 16 bytes) instead of String refs
- Settings chain: updated_by column → Uuid (was text, caused setup crash)
- Removed ~650 lines of String↔Uuid conversion boilerplate
- Eliminates per-request heap allocations for ID cloning
- 16-byte binary comparison vs 36-byte string comparison in all queries
- Native UUID indexing in PostgreSQL (btree on 16 bytes vs 36-char text)

85 files changed, 1090 insertions(+), 1739 deletions(-)

src/domain/repositories/share_repository.rs

@@ -1,4 +1,5 @@
 use thiserror::Error;
+use uuid::Uuid;
 
 use crate::domain::{
     entities::share::{Share, ShareItemType},
@@ -24,7 +25,7 @@ pub trait ShareRepository: Send + Sync + 'static {
     async fn save(&self, share: &Share) -> Result<Share, ShareRepositoryError>;
 
     /// Find a share by its ID
-    async fn find_by_id(&self, id: &str) -> Result<Share, ShareRepositoryError>;
+    async fn find_by_id(&self, id: Uuid) -> Result<Share, ShareRepositoryError>;
 
     /// Find a share by its token
     async fn find_by_token(&self, token: &str) -> Result<Share, ShareRepositoryError>;
@@ -37,10 +38,10 @@ pub trait ShareRepository: Send + Sync + 'static {
     ) -> Result<Vec<Share>, ShareRepositoryError>;
 
     /// Delete a share by its ID
-    async fn delete(&self, id: &str) -> Result<(), ShareRepositoryError>;
+    async fn delete(&self, id: Uuid) -> Result<(), ShareRepositoryError>;
 
     /// Find all shares created by a specific user
-    async fn find_by_user(&self, user_id: &str) -> Result<Vec<Share>, ShareRepositoryError>;
+    async fn find_by_user(&self, user_id: Uuid) -> Result<Vec<Share>, ShareRepositoryError>;
 
     /// Find all shares (admin operation)
     async fn find_all(&self) -> Result<Vec<Share>, ShareRepositoryError>;