feat(ecosystem): adopt hub-core dependency and CI pin gate (CORE-WP-0009)

Import slugify_or_default from hub-core, add contract tests, vendor hub-core in
Docker/Forgejo CI, document metadata isolation and pagination deferral, and
align INTENT/SCOPE with three-repo stack.

src/core_hub/api/v2.py

@@ -1,7 +1,8 @@
 import json
-import re
 from typing import Annotated, Any
 
+from hub_core.utils.slugs import slugify_or_default
+
 from fastapi import APIRouter, Depends, Query, Request, status
 from fastapi.responses import PlainTextResponse, RedirectResponse
 from sqlalchemy import select
@@ -31,11 +32,6 @@ TokenDependency = Annotated[str, Depends(require_api_token)]
 SessionDependency = Annotated[AsyncSession, Depends(session_scope)]
 
 
-def slugify(value: str) -> str:
-    slug = re.sub(r"[^a-z0-9]+", "-", value.lower()).strip("-")
-    return slug or "resource"
-
-
 def encode_body(payload: dict[str, Any]) -> str:
     return json.dumps(payload, sort_keys=True)
 
@@ -246,7 +242,7 @@ async def create_api_consumer(
     body: dict[str, Any], _: TokenDependency, session: SessionDependency
 ) -> dict[str, Any]:
     row = ApiConsumer(
-        slug=body.get("slug") or slugify(body["name"]),
+        slug=body.get("slug") or slugify_or_default(body["name"]),
         name=body["name"],
         description=body.get("description"),
         hub_capability_manifest_id=body.get("hubCapabilityManifestId"),