Add CSV file upload and auto-delimiter detection for pilot import

Allows uploading a CSV file directly instead of only pasting text, and
auto-detects comma vs semicolon separators to support more locales.

web/competition.js

@@ -953,15 +953,33 @@
   function openImportModal() {
     const backdrop = el("div", { class: "modal-backdrop",
       onclick: (e) => { if (e.target === backdrop) backdrop.remove(); } });
+    let selectedFile = null;
+    const fileNameSpan = el("span", { class: "muted small", style: { marginLeft: "0.5rem" } }, "");
+    const fileInput = el("input", { type: "file", accept: ".csv,text/csv", style: { display: "none" },
+      onchange: (e) => {
+        selectedFile = e.target.files[0] || null;
+        fileNameSpan.textContent = selectedFile ? selectedFile.name : "";
+      },
+    });
     const textarea = el("textarea", { placeholder: t("csv_paste"), style: { width: "100%", minHeight: "180px" } });
     backdrop.appendChild(el("div", { class: "modal" },
       el("h3", null, t("import_csv")),
+      el("p", { class: "muted small", style: { marginBottom: "0.5rem" } }, t("csv_separator_hint")),
+      el("div", { style: { marginBottom: "0.75rem", display: "flex", alignItems: "center" } },
+        fileInput,
+        el("button", { onclick: () => fileInput.click() }, t("upload_file")),
+        fileNameSpan,
+      ),
       textarea,
       el("div", { class: "row", style: { justifyContent: "flex-end", marginTop: "1rem" } },
         el("button", { onclick: () => backdrop.remove() }, t("cancel")),
         el("button", { class: "primary", onclick: async () => {
           try {
-            await API.importPilots(competitionId, textarea.value);
+            const data = selectedFile || textarea.value;
+            if (!data || (typeof data === "string" && !data.trim())) {
+              alert(t("csv_empty")); return;
+            }
+            await API.importPilots(competitionId, data);
             await loadPilots();
             backdrop.remove();
             render();