Complete Better Auth migration, harden security, update all docs

Console:
- Rewrite auth from JWT decoding to Better Auth useSession()
- Add auth-client.ts with createAuthClient
- Remove elydora_token localStorage, dead auth API functions
- Fix login/register pages to use signIn.email/signUp.email

Server:
- Upgrade better-auth ^1.2.0 → ^1.5.5
- CORS: enforce allowlist on all environments
- Sync auth service and middleware with backend

SDKs:
- Deprecate login/register in Node, Python, Go SDKs
- Update READMEs to show direct token initialization

Config:
- Sanitize .env with dev-only placeholder values
- Update helm chart and install scripts

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/console/src/lib/auth-client.ts

@@ -0,0 +1,11 @@
+import { createAuthClient } from 'better-auth/react';
+import { organizationClient } from 'better-auth/client/plugins';
+
+export const authClient = createAuthClient({
+  baseURL: process.env.NEXT_PUBLIC_API_BASE_URL || 'http://localhost:8787',
+  plugins: [
+    organizationClient(),
+  ],
+});
+
+export const { signIn, signUp, signOut, useSession } = authClient;