feat(manager-core): admin auth gate (Phase 3a)

Closes the regression risk of the admin API and dashboard being open
to anyone reaching the bound port. Required foundation before v1.1
data-plane services land.

Per-user accounts (admin_users), Argon2id passwords, env-var bootstrap
of the first admin that becomes inert once any admin exists, opaque
32-byte session token doubling as bearer credential, 24h sliding TTL
configurable via PICLOUD_SESSION_TTL_HOURS. is_active column lets
admins be deactivated without losing audit history; last-active-admin
guard on DELETE and on PATCH that flips is_active to false (sessions
also wiped on deactivation).

require_admin middleware fronts every /api/v1/admin/* route. The data
plane (/api/v1/execute/{id}), /healthz, /version, and user routes
stay open. picloud admin reset-password <username> subcommand handles
recovery without going through HTTP.

Dashboard gains /admin/login and /admin/admins surfaces, a top-bar
user menu, and a token store with a localStorage echo so refreshes
don't sign you out. Cookie-based auth works in parallel for non-SPA
clients.

Forward compatibility: future RBAC tables (admin_roles,
admin_user_roles) join on admin_users.id; the auth middleware is the
seam where role checks slot in. Email, 2FA, passkeys, and personal
API tokens are all additive without touching admin_users.

Blueprint §11.4 updated to reflect what actually shipped.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

dashboard/src/lib/api.ts

@@ -5,6 +5,11 @@
 // the same Caddy upstream so the "Test invoke" panel can hit it
 // without any cross-origin gymnastics.
 
+import { goto } from '$app/navigation';
+import { base } from '$app/paths';
+import { browser } from '$app/environment';
+import { clearSession, getToken, setSession, type AdminUser } from './auth';
+
 export interface ScriptSandbox {
 	max_operations?: number;
 	max_string_size?: number;
@@ -134,12 +139,26 @@ export class ApiError extends Error {
 }
 
 async function adminRequest<T>(path: string, init?: RequestInit): Promise<T> {
-	const res = await fetch(path, {
-		...init,
-		headers: { 'content-type': 'application/json', ...(init?.headers ?? {}) }
-	});
+	const headers: Record<string, string> = {
+		'content-type': 'application/json',
+		...((init?.headers as Record<string, string>) ?? {})
+	};
+	const tok = getToken();
+	if (tok && !headers['authorization']) {
+		headers['authorization'] = `Bearer ${tok}`;
+	}
+	const res = await fetch(path, { ...init, headers });
 	const text = await res.text();
 	const parsed: unknown = text ? safeJson(text) : null;
+	if (res.status === 401) {
+		// Token gone stale or never present. Drop any cached session
+		// and bounce to login — unless we're already on it, in which
+		// case throw and let the login form render the error.
+		clearSession();
+		if (browser && !window.location.pathname.endsWith('/login')) {
+			void goto(`${base}/login`);
+		}
+	}
 	if (!res.ok) {
 		const message =
 			(parsed && typeof parsed === 'object' && 'error' in parsed
@@ -158,11 +177,76 @@ function safeJson(text: string): unknown {
 	}
 }
 
+export interface AdminUserRecord {
+	id: string;
+	username: string;
+	is_active: boolean;
+	created_at: string;
+	last_login_at: string | null;
+}
+
+export interface CreateAdminInput {
+	username: string;
+	password: string;
+}
+
+export interface PatchAdminInput {
+	username?: string;
+	password?: string;
+	is_active?: boolean;
+}
+
+interface LoginResponse {
+	user: AdminUser;
+	token: string;
+	expires_at: string;
+}
+
 export const api = {
 	health: () => fetch('/healthz').then((r) => r.text()),
 
 	version: () => adminRequest<VersionInfo>('/version'),
 
+	auth: {
+		login: async (username: string, password: string): Promise<AdminUser> => {
+			const r = await adminRequest<LoginResponse>('/api/v1/admin/auth/login', {
+				method: 'POST',
+				body: JSON.stringify({ username, password })
+			});
+			setSession(r.user, r.token);
+			return r.user;
+		},
+		logout: async (): Promise<void> => {
+			try {
+				await adminRequest<null>('/api/v1/admin/auth/logout', { method: 'POST' });
+			} finally {
+				// Always clear locally — logout is idempotent server-side
+				// and we don't want a network blip to strand the SPA in
+				// a "logged out on server, still logged in client-side"
+				// state.
+				clearSession();
+			}
+		},
+		me: () => adminRequest<AdminUser>('/api/v1/admin/auth/me')
+	},
+
+	admins: {
+		list: () => adminRequest<AdminUserRecord[]>('/api/v1/admin/admins'),
+		get: (id: string) => adminRequest<AdminUserRecord>(`/api/v1/admin/admins/${id}`),
+		create: (input: CreateAdminInput) =>
+			adminRequest<AdminUserRecord>('/api/v1/admin/admins', {
+				method: 'POST',
+				body: JSON.stringify(input)
+			}),
+		update: (id: string, input: PatchAdminInput) =>
+			adminRequest<AdminUserRecord>(`/api/v1/admin/admins/${id}`, {
+				method: 'PATCH',
+				body: JSON.stringify(input)
+			}),
+		remove: (id: string) =>
+			adminRequest<null>(`/api/v1/admin/admins/${id}`, { method: 'DELETE' })
+	},
+
 	routes: {
 		listForScript: (scriptId: string) =>
 			adminRequest<Route[]>(`/api/v1/admin/scripts/${scriptId}/routes`),