fix(mana-auth): /api/v1/auth/login uses wrong cookie name in production

The custom /api/v1/auth/login route signs the user in via the
better-auth SDK (auth.api.signInEmail) and then forges a request to
/api/auth/token to mint a JWT, passing the session token as a synthetic
cookie header.

The cookie name was hardcoded as `mana.session_token=...`, but in
production better-auth issues the session cookie with the __Secure-
prefix (because secure: true is enabled). Get-session middleware on the
/api/auth/token side couldn't find the session under the unprefixed
name, so it returned 401 silently. Result: tokenResponse.ok was false,
the route fell through, and the response had no `accessToken` field at
all — only the bare { token, user, redirect } from signInEmail.

The frontend in @mana/shared-auth then picked this up as
`data.accessToken === undefined` and stored undefined as the JWT, while
the parallel /api/auth/sign-in/email call masked the visible damage by
setting the SSO cookie. So login *appeared* to work in the browser
(cookie present, session worked) but the JWT path was always broken.

Fix: pick the cookie name based on config.nodeEnv. In production use
__Secure-mana.session_token, in development use mana.session_token (no
__Secure- prefix because secure: false in dev).

Verified end-to-end on auth.mana.how:
  POST /api/v1/auth/login → response now includes accessToken (a real
  JWT, EdDSA, with sub/email/role/sid/tier/iss/aud claims), refreshToken
  (the session token), plus the original signInEmail fields.

The other /api/auth/get-session call sites in this file forward the
incoming request headers verbatim, so they preserve whatever real cookie
the browser sent and don't have this bug.

services/mana-auth/src/routes/auth.ts

@@ -120,13 +120,22 @@ export function createAuthRoutes(
 			}
 
 			// signInEmail returns { token (session token), user, redirect }
-			// Use the session token to call Better Auth's JWT /token endpoint
+			// Use the session token to call Better Auth's JWT /token endpoint.
+			//
+			// In production Better Auth issues the session cookie with the
+			// __Secure- prefix (because secure: true is set), so we have to
+			// pass that exact cookie name back when forging the request to
+			// /api/auth/token. Without the prefix the get-session middleware
+			// can't find the session and the JWT mint silently fails — the
+			// route falls through and returns a response without accessToken.
 			const sessionToken = response?.token;
 			if (sessionToken) {
+				const cookieName =
+					config.nodeEnv === 'production' ? '__Secure-mana.session_token' : 'mana.session_token';
 				const tokenResponse = await auth.handler(
 					new Request(new URL('/api/auth/token', config.baseUrl), {
 						method: 'GET',
-						headers: new Headers({ cookie: `mana.session_token=${sessionToken}` }),
+						headers: new Headers({ cookie: `${cookieName}=${sessionToken}` }),
 					})
 				);