Fix: Use user's home directory for temporary uploads instead of /tmp

The /tmp directory often doesn't allow web servers to create subdirectories. Now uses:
- Config admin: ~/.aisbf/temp_uploads/
- Database users: ~/.aisbf/user_auth_files/{user_id}/temp_uploads/

This ensures uploads work in all environments including restrictive web server configurations.

main.py

@@ -5724,8 +5724,13 @@ async def dashboard_provider_upload_chunk(
         upload_id = hashlib.sha256(f"{current_user_id}:{provider_key}:{file_name}:{total_size}".encode()).hexdigest()[:16]
         file_ext = Path(file_name).suffix if file_name else '.bin'
 
-        # Create temporary upload directory
-        temp_dir = Path('/tmp/aisbf_uploads')
+        # Create temporary upload directory in user's home
+        if is_config_admin:
+            # Config admin: use their home directory
+            temp_dir = Path.home() / '.aisbf' / 'temp_uploads'
+        else:
+            # Database user: use their auth files directory
+            temp_dir = get_user_auth_files_dir(current_user_id) / 'temp_uploads'
         temp_dir.mkdir(parents=True, exist_ok=True)
 
         # Save chunk

templates/dashboard/providers.html

@@ -136,8 +136,8 @@ along with this program.  If not, see <https://www.gnu.org/licenses/>.
 let providersData = {{ providers_json | safe }};
 let expandedProviders = new Set();
 
-// Chunk size: 1MB chunks for maximum compatibility with all proxies
-const CHUNK_SIZE = 1 * 1024 * 1024;
+// Chunk size: 512KB chunks for maximum compatibility with restrictive proxies
+const CHUNK_SIZE = 512 * 1024;
 
 // Generic chunked upload handler for all providers
 async function uploadFileChunked(providerKey, fileType, file, configObject) {