feat(settings): panel-tunable feature flags

Add a Feature Flags card to the Settings page that toggles env-gated
subsystems (external/internal PR review, web research, strategy engine,
pitch provisioning, RAG auto-update, transcript pruning) directly from
the panel instead of hand-editing environment variables.

Flags persist in system_settings as 'true'/'false' and are overlaid onto
the live config singleton at startup; an unset flag keeps its
environment/config default. A toggle takes effect on the next backend
restart — no per-consumer re-routing.

Backend: FEATURE_FLAGS registry + bool validator + get_bool accessor on
SettingsService; feature_flag_effective_values and
apply_persisted_feature_flags; GET /settings/feature-flags; best-effort
startup overlay in the app lifespan.

Frontend: settingsApi.getFeatureFlags / setFeatureFlag and a
FeatureFlagsCard rendered full-width below the settings grid.

panel/src/app/(dashboard)/settings/page.tsx

@@ -27,6 +27,7 @@ import {
 import { toast } from "sonner";
 import { API_URL, WS_URL } from "@/lib/constants";
 import { TranscriptRetentionCard } from "@/components/settings/transcript-retention-card";
+import { FeatureFlagsCard } from "@/components/settings/feature-flags-card";
 
 export default function SettingsPage() {
   const { theme, setTheme } = useTheme();
@@ -241,6 +242,10 @@ export default function SettingsPage() {
         </Card>
       </div>
 
+      {/* Feature Flags — master switches for optional subsystems (full width;
+          persisted server-side, applied on next restart). */}
+      <FeatureFlagsCard />
+
       {/* Save Button */}
       <div className="flex justify-end">
         <Button onClick={handleSave}>

panel/src/components/settings/feature-flags-card.tsx

@@ -0,0 +1,100 @@
+"use client";
+
+import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
+import { settingsApi } from "@/lib/api";
+import type { FeatureFlag } from "@/lib/api/settings";
+import {
+  Card,
+  CardContent,
+  CardDescription,
+  CardHeader,
+  CardTitle,
+} from "@/components/ui/card";
+import { Label } from "@/components/ui/label";
+import { Switch } from "@/components/ui/switch";
+import { Separator } from "@/components/ui/separator";
+import { Flag } from "lucide-react";
+import { toast } from "sonner";
+
+// One-line blurb per flag so the operator knows what each master switch gates.
+const FLAG_DESCRIPTIONS: Record<string, string> = {
+  external_pr_enabled: "Discover and review inbound external/fork pull requests.",
+  internal_pr_enabled: "Run the read-only safety reviewer on internal branch PRs.",
+  research_enabled: "Let the Board and PMs run web research.",
+  strategy_engine_enabled: "Generate and maintain company strategy artifacts.",
+  provisioning_enabled: "Auto-provision projects from approved pitches.",
+  rag_auto_update_enabled: "Keep the knowledge base index refreshed automatically.",
+  transcript_prune_enabled: "Run the background sweep that prunes old transcripts.",
+};
+
+export function FeatureFlagsCard() {
+  const queryClient = useQueryClient();
+
+  const { data, isLoading } = useQuery({
+    queryKey: ["feature-flags"],
+    queryFn: settingsApi.getFeatureFlags,
+  });
+
+  const toggleMutation = useMutation({
+    mutationFn: ({ key, enabled }: { key: string; enabled: boolean }) =>
+      settingsApi.setFeatureFlag(key, enabled),
+    onSuccess: (_data, { enabled }) => {
+      queryClient.invalidateQueries({ queryKey: ["feature-flags"] });
+      toast.success(
+        `Feature ${enabled ? "enabled" : "disabled"} — takes effect on next restart`,
+      );
+    },
+    onError: (error) => {
+      toast.error(
+        `Failed to update: ${error instanceof Error ? error.message : "Unknown error"}`,
+      );
+    },
+  });
+
+  const flags: FeatureFlag[] = data?.flags ?? [];
+  const note = data?.note ?? "Changes take effect on the next backend restart.";
+
+  return (
+    <Card>
+      <CardHeader>
+        <CardTitle className="flex items-center gap-2">
+          <Flag className="h-5 w-5" />
+          Feature Flags
+        </CardTitle>
+        <CardDescription>
+          Master switches for optional subsystems. Unset flags fall back to the
+          environment default. {note}
+        </CardDescription>
+      </CardHeader>
+      <CardContent className="space-y-4">
+        {isLoading && (
+          <p className="text-sm text-muted-foreground">Loading feature flags…</p>
+        )}
+        {!isLoading && flags.length === 0 && (
+          <p className="text-sm text-muted-foreground">No feature flags available.</p>
+        )}
+        {flags.map((flag, i) => (
+          <div key={flag.key}>
+            {i > 0 && <Separator className="mb-4" />}
+            <div className="flex items-center justify-between gap-4">
+              <div className="min-w-0">
+                <Label htmlFor={`flag-${flag.key}`}>{flag.label}</Label>
+                <p className="text-sm text-muted-foreground">
+                  {FLAG_DESCRIPTIONS[flag.key] ?? flag.key}
+                </p>
+              </div>
+              <Switch
+                id={`flag-${flag.key}`}
+                checked={flag.enabled}
+                disabled={toggleMutation.isPending}
+                onCheckedChange={(checked) =>
+                  toggleMutation.mutate({ key: flag.key, enabled: checked })
+                }
+              />
+            </div>
+          </div>
+        ))}
+      </CardContent>
+    </Card>
+  );
+}

panel/src/lib/api/settings.ts

@@ -4,6 +4,17 @@ export interface SettingsResponse {
   settings: Record<string, string>;
 }
 
+export interface FeatureFlag {
+  key: string;
+  label: string;
+  enabled: boolean;
+}
+
+export interface FeatureFlagsResponse {
+  flags: FeatureFlag[];
+  note: string;
+}
+
 export const settingsApi = {
   // GET /api/settings — all runtime-editable settings as a flat key→value map.
   getAll: async (): Promise<Record<string, string>> => {
@@ -15,4 +26,13 @@ export const settingsApi = {
     const { data } = await api.put<SettingsResponse>(`/settings/${key}`, { value });
     return data.settings;
   },
+  // GET /api/settings/feature-flags — effective flag values (override, else env).
+  getFeatureFlags: async (): Promise<FeatureFlagsResponse> => {
+    const { data } = await api.get<FeatureFlagsResponse>("/settings/feature-flags");
+    return data;
+  },
+  // PUT /api/settings/{key} — persist a feature flag as "true"/"false".
+  setFeatureFlag: async (key: string, enabled: boolean): Promise<void> => {
+    await api.put<SettingsResponse>(`/settings/${key}`, { value: enabled ? "true" : "false" });
+  },
 };