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>

sdks/python/elydora/cli.py

@@ -172,7 +172,7 @@ def build_parser() -> argparse.ArgumentParser:
     install_parser.add_argument("--agent_id", required=True, help="Agent ID")
     install_parser.add_argument("--private_key", required=True, help="Base64url-encoded Ed25519 private key seed")
     install_parser.add_argument("--kid", required=True, help="Key ID")
-    install_parser.add_argument("--token", default="", help="JWT bearer token (optional)")
+    install_parser.add_argument("--token", default="", help="API bearer token (optional)")
     install_parser.add_argument("--base_url", default="https://api.elydora.com", help="API base URL")
 
     # uninstall