Add persistent default temp directory setting with web UI

- Add settings.json persistence (load/save) in backend
- Add GET/POST /api/settings endpoints for default_temp_dir
- Add Default Temp Directory config UI in Temporary Storage section
- Auto-fallback: jobs use saved default if no per-job temp_dir set
- Per-job Advanced Options placeholder syncs with saved default
- Add settings.json to .gitignore for per-machine config

static/app.js

@@ -2122,6 +2122,55 @@ async function initializeApp() {
 
     // Load initial temp info
     loadTempInfo();
+
+    // Default temp directory setting
+    const saveTempDirBtn = document.getElementById("save-temp-dir-btn");
+    const defaultTempDirInput = document.getElementById("default-temp-dir-input");
+    const tempDirStatus = document.getElementById("temp-dir-status");
+
+    // Load saved default temp dir on init
+    loadDefaultTempDir();
+
+    if (saveTempDirBtn) {
+        saveTempDirBtn.addEventListener("click", async () => {
+            const newDir = defaultTempDirInput ? defaultTempDirInput.value.trim() : "";
+            tempDirStatus.textContent = "";
+            tempDirStatus.style.color = "";
+            saveTempDirBtn.disabled = true;
+            saveTempDirBtn.innerHTML = '<i class="fa-solid fa-spinner fa-spin"></i> Saving...';
+            try {
+                const res = await fetch("/api/settings", {
+                    method: "POST",
+                    headers: { "Content-Type": "application/json" },
+                    body: JSON.stringify({ default_temp_dir: newDir })
+                });
+                if (res.ok) {
+                    tempDirStatus.style.color = "var(--success, #4caf50)";
+                    tempDirStatus.textContent = newDir
+                        ? `\u2713 Default temp directory saved: ${newDir}`
+                        : "\u2713 Reset to project default temp/ directory.";
+                    // Also update the per-job input placeholder/value
+                    const perJobInput = document.getElementById("temp-dir-input");
+                    if (perJobInput && !perJobInput.value.trim()) {
+                        perJobInput.placeholder = newDir
+                            ? `Default: ${newDir} (override here)`
+                            : "e.g. /mnt/fast_ssd/temp (Leave empty for default temp/)";
+                    }
+                } else {
+                    const errData = await res.json().catch(() => ({}));
+                    tempDirStatus.style.color = "var(--danger, #f44336)";
+                    tempDirStatus.textContent = `\u2717 ${errData.detail || "Failed to save setting."}`;
+                }
+            } catch (err) {
+                tempDirStatus.style.color = "var(--danger, #f44336)";
+                tempDirStatus.textContent = "\u2717 Network error saving setting.";
+                console.error(err);
+            } finally {
+                saveTempDirBtn.disabled = false;
+                saveTempDirBtn.innerHTML = '<i class="fa-solid fa-floppy-disk"></i> Save';
+            }
+        });
+    }
 }
 
 async function loadTempInfo() {
@@ -2220,4 +2269,22 @@ async function loadTempInfo() {
     }
 }
 
+async function loadDefaultTempDir() {
+    try {
+        const res = await fetch("/api/settings");
+        if (!res.ok) return;
+        const settings = await res.json();
+        const savedDir = settings.default_temp_dir || "";
+        const defaultInput = document.getElementById("default-temp-dir-input");
+        if (defaultInput) defaultInput.value = savedDir;
+        // Update per-job input placeholder
+        const perJobInput = document.getElementById("temp-dir-input");
+        if (perJobInput && savedDir && !perJobInput.value.trim()) {
+            perJobInput.placeholder = `Default: ${savedDir} (override here)`;
+        }
+    } catch (err) {
+        console.error("Failed to load settings:", err);
+    }
+}
+
 initializeApp();