Fix PR review comments on cookie banner branding

- Add scope parameter to UpdateShowBranding to prevent cross-tenant updates
- Use cmd.Context() instead of context.Background() in proboctl CLI
- Drop SQL column default after backfill in migration
- Add bounds check for int-to-int32 conversion in PG_POOL_SIZE
- Update branding link to getprobo.com homepage

Signed-off-by: Émile Ré <emile@getprobo.com>

pkg/coredata/migrations/20260422T120000Z.sql

@@ -13,3 +13,4 @@
 -- PERFORMANCE OF THIS SOFTWARE.
 
 ALTER TABLE cookie_banners ADD COLUMN show_branding BOOLEAN NOT NULL DEFAULT TRUE;
+ALTER TABLE cookie_banners ALTER COLUMN show_branding DROP DEFAULT;