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/infrastructure/services/path_resolver_service.rs

@@ -7,6 +7,7 @@
 
 use sqlx::PgPool;
 use std::sync::Arc;
+use uuid::Uuid;
 
 use crate::application::dtos::display_helpers::{
     category_for, format_file_size, icon_class_for, icon_special_class_for,
@@ -39,7 +40,7 @@ impl PathResolverService {
     pub async fn resolve_path_for_user(
         &self,
         path: &str,
-        user_id: &str,
+        user_id: Uuid,
     ) -> Result<ResolvedResource, DomainError> {
         let path = path.trim_start_matches('/').trim_end_matches('/');
         if path.is_empty() {
@@ -180,7 +181,7 @@ impl PathResolverService {
     }
 
     /// Returns `true` if the resource at `path` belongs to `user_id`.
-    pub async fn exists_for_user(&self, path: &str, user_id: &str) -> Result<bool, DomainError> {
+    pub async fn exists_for_user(&self, path: &str, user_id: Uuid) -> Result<bool, DomainError> {
         let path = path.trim_start_matches('/').trim_end_matches('/');
         if path.is_empty() {
             return Ok(false);