feat(FN-1265): add agent budget settings UI and API

- Add Budget Settings section to ConfigTab with token limit, usage threshold, budget period, and reset day inputs
- Add budget usage badge to DashboardTab showing token consumption and threshold warning
- Add budget API functions to api.ts (getBudgetSummary, updateBudgetConfig, deleteBudgetUsage)
- Add budget routes to routes.ts for GET/PATCH/DELETE agent budget endpoints
- Add CSS styles for budget progress bar, warning indicators, and section layout
- Add comprehensive tests for budget UI components and API routes

packages/dashboard/app/api.ts

@@ -1975,8 +1975,9 @@ import type {
   AgentReflection,
   AgentPerformanceSummary,
   ReflectionTrigger,
+  AgentBudgetStatus,
 } from "@fusion/core";
-export type { Agent, AgentDetail, AgentCapability, AgentState, AgentHeartbeatEvent, AgentHeartbeatRun, AgentCreateInput, AgentUpdateInput, AgentTaskSession, AgentStats, HeartbeatInvocationSource, OrgTreeNode, AgentReflection, AgentPerformanceSummary, ReflectionTrigger };
+export type { Agent, AgentDetail, AgentCapability, AgentState, AgentHeartbeatEvent, AgentHeartbeatRun, AgentCreateInput, AgentUpdateInput, AgentTaskSession, AgentStats, HeartbeatInvocationSource, OrgTreeNode, AgentReflection, AgentPerformanceSummary, ReflectionTrigger, AgentBudgetStatus };
 
 function withProjectId(path: string, projectId?: string): string {
   if (!projectId) return path;
@@ -3799,6 +3800,20 @@ export function deleteAgentRating(agentId: string, ratingId: string, projectId?:
   });
 }
 
+// ── Agent Budget API ──────────────────────────────────────────────────────
+
+/** Fetch budget status for an agent */
+export function fetchAgentBudgetStatus(agentId: string, projectId?: string): Promise<AgentBudgetStatus> {
+  return api<AgentBudgetStatus>(withProjectId(`/agents/${encodeURIComponent(agentId)}/budget`, projectId));
+}
+
+/** Reset budget usage for an agent */
+export function resetAgentBudget(agentId: string, projectId?: string): Promise<void> {
+  return api<void>(withProjectId(`/agents/${encodeURIComponent(agentId)}/budget/reset`, projectId), {
+    method: "POST",
+  });
+}
+
 // ── Plugin Management ────────────────────────────────────────────────────────
 
 /** Fetch all installed plugins */