feat: folder ownership scoping, batch operations integration, frontend audit fixes

Backend:
- Add owner_id to Folder entity + FolderDto (DB user_id column)
- Add list_folders_by_owner to FolderRepository trait + PG impl
- Add list_folders_for_owner to FolderUseCase + FolderService
- Rewrite FolderHandler: all endpoints now scope by AuthUser
- Remove dead handler methods (list_folders_inner, list_folders_for_user, is_user_home_folder, folder_belongs_to_user)
- Add ownership check in get_folder (returns 404 on mismatch)

Batch operations:
- Add trash_service + zip_service to BatchOperationService
- New methods: trash_files, trash_folders, move_folders, download_zip
- New handlers: trash_batch, move_folders_batch, download_batch
- New routes: POST /api/batch/trash, /api/batch/folders/move, /api/batch/download

Frontend:
- Replace findUserHomeFolder (~130 lines) with resolveHomeFolder (~35 lines)
- Remove client-side folder filtering in loadFiles (backend now scopes)
- Rewrite batchDelete: N requests -> 1 POST /api/batch/trash
- Rewrite batchMove: N requests -> 2 POST max (files + folders)
- Rewrite batchDownload: N requests -> 1 POST /api/batch/download (ZIP)
- Search moved to backend, share system uses backend API
- Dark mode fixes, frontend audit improvements

src/application/ports/inbound.rs

@@ -3,7 +3,9 @@ use async_trait::async_trait;
 use crate::application::dtos::folder_dto::{
     CreateFolderDto, FolderDto, MoveFolderDto, RenameFolderDto,
 };
-use crate::application::dtos::search_dto::{SearchCriteriaDto, SearchResultsDto};
+use crate::application::dtos::search_dto::{
+    SearchCriteriaDto, SearchResultsDto, SearchSuggestionsDto,
+};
 use crate::common::errors::DomainError;
 
 /// Primary port for folder operations
@@ -21,6 +23,14 @@ pub trait FolderUseCase: Send + Sync + 'static {
     /// Lists folders within a parent folder
     async fn list_folders(&self, parent_id: Option<&str>) -> Result<Vec<FolderDto>, DomainError>;
 
+    /// Lists folders scoped to a specific owner (for user-facing endpoints).
+    /// At root level, only returns folders belonging to this user.
+    async fn list_folders_for_owner(
+        &self,
+        parent_id: Option<&str>,
+        owner_id: &str,
+    ) -> Result<Vec<FolderDto>, DomainError>;
+
     /// Lists folders with pagination
     async fn list_folders_paginated(
         &self,
@@ -40,25 +50,24 @@ pub trait FolderUseCase: Send + Sync + 'static {
 }
 
 /**
- * Primary port for file and folder search
+ * Primary port for file and folder search.
  *
- * Defines the operations related to advanced search of
- * files and folders based on various criteria.
+ * All search processing (filtering, scoring, sorting, categorization)
+ * is handled server-side in Rust for maximum efficiency.
  */
 #[async_trait]
 pub trait SearchUseCase: Send + Sync + 'static {
-    /**
-     * Performs a search based on the specified criteria
-     *
-     * @param criteria Search criteria including text, dates, sizes, etc.
-     * @return Search results containing matching files and folders
-     */
+    /// Performs a full search based on the specified criteria.
     async fn search(&self, criteria: SearchCriteriaDto) -> Result<SearchResultsDto, DomainError>;
 
-    /**
-     * Clears the search results cache
-     *
-     * @return Result indicating success or error
-     */
+    /// Returns quick suggestions for autocomplete (lightweight, fast).
+    async fn suggest(
+        &self,
+        query: &str,
+        folder_id: Option<&str>,
+        limit: usize,
+    ) -> Result<SearchSuggestionsDto, DomainError>;
+
+    /// Clears the search results cache.
     async fn clear_search_cache(&self) -> Result<(), DomainError>;
 }