catalog: trust the real signing key

Adds the Ed25519 public key generated by the Catalog Console (#62),
replacing the b"\x00"*32 placeholder, and imports base64 (the key line
referenced it without the import, so bcc_core failed to load at all).

Verified end to end against the signature the Console pushed in b08cf21:
signature verifies, catalog validates clean, resolve_catalog accepts the
bundled copy (19 servers), and a single-byte tamper is rejected.

bcc_core.py

@@ -13,6 +13,7 @@ in its original position.
 
 from __future__ import annotations
 
+import base64
 import contextlib
 import difflib
 import functools
@@ -2168,7 +2169,7 @@ CATALOG_ALLOWED_COMMANDS = frozenset({"npx", "uvx", "docker", "node", "python",
 # still trust an older key: verify_catalog_signature() accepts a match
 # against ANY key in this list.
 CATALOG_PUBKEYS: list[bytes] = [
-    b"\x00" * 32,  # TODO: real key from Catalog Console (#62)
+    base64.b64decode("082NOwVB7uURkvfyS3+knJ+40Fk6C9unsF47+2uPKo4="),
 ]
 
 # Domain-separation prefix for the signed message. The signature covers