Fix: Reduce chunk size to 1MB for maximum proxy compatibility

5MB chunks were still hitting reverse proxy limits for some configurations. 1MB is universally supported and will work with nginx, Cloudflare, and all other reverse proxies with default configurations.

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: 5MB chunks for large files
-const CHUNK_SIZE = 5 * 1024 * 1024;
+// Chunk size: 1MB chunks for maximum compatibility with all proxies
+const CHUNK_SIZE = 1 * 1024 * 1024;
 
 // Generic chunked upload handler for all providers
 async function uploadFileChunked(providerKey, fileType, file, configObject) {