feat(web): add widget config dialog and layout management controls

Add per-widget configuration dialog (WidgetConfigDialog) with settings
infrastructure ready for future configSchema-based forms. Add layout
management controls: reset to default, edit/done toggle, and widget
gear icon for configuration. Wire onEditWidget through WidgetGrid to
BaseWidget.

Implements TW-WDG-004 and TW-WDG-005.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/web/src/app/(authenticated)/page.tsx

@@ -5,6 +5,7 @@ import type { ReactElement } from "react";
 import type { WidgetPlacement } from "@mosaic/shared";
 import { WidgetGrid } from "@/components/widgets/WidgetGrid";
 import { WidgetPicker } from "@/components/widgets/WidgetPicker";
+import { WidgetConfigDialog } from "@/components/widgets/WidgetConfigDialog";
 import { DEFAULT_LAYOUT } from "@/components/widgets/defaultLayout";
 import { fetchDefaultLayout, createLayout, updateLayout } from "@/lib/api/layouts";
 import { useWorkspaceId } from "@/lib/hooks";
@@ -15,6 +16,7 @@ export default function DashboardPage(): ReactElement {
   const [layoutId, setLayoutId] = useState<string | null>(null);
   const [isEditing, setIsEditing] = useState(false);
   const [isPickerOpen, setIsPickerOpen] = useState(false);
+  const [configWidgetId, setConfigWidgetId] = useState<string | null>(null);
   const [isLoading, setIsLoading] = useState(true);
 
   // Debounce timer for auto-saving layout changes
@@ -106,6 +108,15 @@ export default function DashboardPage(): ReactElement {
     [layout, saveLayout]
   );
 
+  const handleResetLayout = useCallback((): void => {
+    setLayout(DEFAULT_LAYOUT);
+    saveLayout(DEFAULT_LAYOUT);
+  }, [saveLayout]);
+
+  const handleEditWidget = useCallback((widgetId: string): void => {
+    setConfigWidgetId(widgetId);
+  }, []);
+
   if (isLoading) {
     return (
       <div className="flex items-center justify-center" style={{ minHeight: 400 }}>
@@ -138,24 +149,42 @@ export default function DashboardPage(): ReactElement {
         </h1>
         <div className="flex items-center gap-2">
           {isEditing && (
-            <button
-              onClick={(): void => {
-                setIsPickerOpen(true);
-              }}
-              style={{
-                padding: "6px 14px",
-                borderRadius: "var(--r)",
-                border: "1px solid var(--border)",
-                background: "transparent",
-                color: "var(--text-2)",
-                fontSize: "0.83rem",
-                fontWeight: 500,
-                cursor: "pointer",
-                transition: "all 0.15s ease",
-              }}
-            >
-              + Add Widget
-            </button>
+            <>
+              <button
+                onClick={handleResetLayout}
+                style={{
+                  padding: "6px 14px",
+                  borderRadius: "var(--r)",
+                  border: "1px solid var(--border)",
+                  background: "transparent",
+                  color: "var(--muted)",
+                  fontSize: "0.83rem",
+                  fontWeight: 500,
+                  cursor: "pointer",
+                  transition: "all 0.15s ease",
+                }}
+              >
+                Reset
+              </button>
+              <button
+                onClick={(): void => {
+                  setIsPickerOpen(true);
+                }}
+                style={{
+                  padding: "6px 14px",
+                  borderRadius: "var(--r)",
+                  border: "1px solid var(--border)",
+                  background: "transparent",
+                  color: "var(--text-2)",
+                  fontSize: "0.83rem",
+                  fontWeight: 500,
+                  cursor: "pointer",
+                  transition: "all 0.15s ease",
+                }}
+              >
+                + Add Widget
+              </button>
+            </>
           )}
           <button
             onClick={(): void => {
@@ -184,9 +213,21 @@ export default function DashboardPage(): ReactElement {
         layout={layout}
         onLayoutChange={handleLayoutChange}
         {...(isEditing && { onRemoveWidget: handleRemoveWidget })}
+        {...(isEditing && { onEditWidget: handleEditWidget })}
         isEditing={isEditing}
       />
 
+      {/* Widget config dialog */}
+      {configWidgetId && (
+        <WidgetConfigDialog
+          widgetId={configWidgetId}
+          open
+          onClose={(): void => {
+            setConfigWidgetId(null);
+          }}
+        />
+      )}
+
       {/* Widget picker drawer */}
       <WidgetPicker
         open={isPickerOpen}