Extend the public API: news excerpts/detail, game team logos, sponsor logo dimensions, player licenses

- news: NewsItemOut gains `excerpt` (truncated body); GET /news/{slug}/
  fetches a single item. slug already auto-populates on save, but a
  data migration backfills any pre-existing blank ones.
- games: home_team/away_team change from plain strings to {id, name,
  logo_url} objects -- home links to the actual Team (logo from the
  club's own logo, since teams have none of their own), away links
  to the actual Opponent (which already had a logo field). Breaking
  change for any existing consumer of the old string shape.
- sponsors: SponsorOut gains logo_width/logo_height, computed in
  Sponsor.save() -- Pillow for raster, a bounded regex read of the
  SVG root tag for vector logos (not a full XML parse, since that's
  exposed to entity-expansion attacks on untrusted uploads). A data
  migration backfills dimensions for existing sponsor logos.
- teams: PlayerOut gains `license`, sourced from ClubMembership (not
  Member -- it's per-club, per-season), batched in one query.

club/api.py

@@ -21,6 +21,8 @@ class SponsorOut(Schema):
     id: uuid.UUID
     name: str
     logo_url: str | None
+    logo_width: int | None
+    logo_height: int | None
     url: str | None
     start_date: date
     end_date: date | None
@@ -31,6 +33,8 @@ def _to_sponsor_out(sponsor, request) -> SponsorOut:
         id=sponsor.pk,
         name=sponsor.name,
         logo_url=request.build_absolute_uri(sponsor.logo.url) if sponsor.logo else None,
+        logo_width=sponsor.logo_width,
+        logo_height=sponsor.logo_height,
         url=sponsor.url or None,
         start_date=sponsor.start_date,
         end_date=sponsor.end_date,