feat(audience): warn and drop Identify()/Alias() calls with a malformed passport id

[nattb8]

Summary

Studios sometimes call Identify() or Alias() with IdentityType.Passport but pass their own internal user id instead of a real Passport id, and today nothing catches it, so bad data silently flows into the audience pipeline. This rejects the call (no event sent, UserId untouched) and logs a warning when the id doesn't match the shape Passport actually issues (connection|id or a bare UUID), so studios see the mistake immediately during local testing instead of finding it in the data warehouse later.

Test plan

• Unit tests covering: malformed passport id warns and drops the call (no event enqueued, UserId stays null) for both Identify() and Alias() (either side); valid pipe-form/UUID/whitespace-padded ids and non-passport identity types never warn or drop
• Unit tests confirming a whitespace-padded valid passport id is stored and sent trimmed, not with the padding intact (the id that's validated and the id that's stored/sent must match)
• Sample-app PlayMode test exercising the Identify() rejection through the UI, and fixed existing sample-app tests (Identify and Alias) that used non-Passport-shaped ids under the default Passport identity type
• dotnet build src/Audience.Build/Audience.Tests/Audience.Tests.csproj succeeds with no new warnings
• dotnet test src/Audience.Build/Audience.Tests/Audience.Tests.csproj passes (375 tests, 0 failed)

[github-actions]

Audience SDK — Build Size

Platform	SDK Size	Change
Android	0.37 / 20.00 MB	+0.01 MB	✅
Windows	0.16 / 20.00 MB	+0.00 MB	✅
iOS	8.54 / 20.00 MB	+0.03 MB	✅
macOS	0.92 / 20.00 MB	+0.02 MB	✅

SDK Size = build minus empty app. Change = vs baseline. Fails if any platform exceeds its absolute size limit.