fix: resilient member lookup across Tharga.Team / MongoDB / Blazor / Service

[poxet]

Summary

Resolves #64 — the comprehensive .Single(predicate) sweep that follows up on #59. Drives ThrowMoreThanOneMatchException to zero across the Platform stack when Team.Members or ApiKey collections happen to contain duplicate-keyed rows.

• New public helper Tharga.Team.ResilientMemberLookup with three IEnumerable<T> extensions: PickOneOrDefault (two overloads — team-member-domain and single-context) and ReplaceByReference.
• Replaced .Single / .SingleOrDefault at 13 call sites across TeamRepository (6), TeamServiceBase (4), TeamComponent.razor / TeamInviteView.razor (2), and ApiKeyAdministrationService (2). Each site picks the first match and logs a Warning carrying the team key, lookup key, and match count so duplicates are findable for out-of-band cleanup.
• Fixed the symmetric strip-siblings bug in TeamRepository writes: every former Where(x => x.Key != userKey).Union([member]) is now members.ReplaceByReference(target, updated), so duplicate-keyed siblings are preserved on save rather than silently dropped.
• Promoted the existing internal TeamMemberResolver from Tharga.Team.Blazor into the new public helper; updated 5 razor callers; removed the old helper.

Behaviour change for consumers

• TeamServiceBase and TeamRepository constructors now accept an optional ILogger<> (default null). Existing subclasses (TeamServiceRepositoryBase, custom TeamService implementations) continue to compile without change. Wire AddLogging() in your composition root to capture the new duplicate-row warnings.
• ApiKeyAdministrationService constructor adds an optional ILogger<ApiKeyAdministrationService> parameter (default null).

Out of scope

• Self-healing (deleting duplicate rows during read) — deferred until/unless symptoms persist.
• UserServiceBase.GetUserAsync race (#65) — separate feature.

Test plan

• dotnet build -c Release — 0 warnings, 0 errors
• dotnet test -c Release — 289 / 289 passing (14 new tests)
• ResilientMemberLookupTests (10 tests) — both PickOneOrDefault overloads and ReplaceByReference, including the strip-siblings preservation test
• ResilientLookupCallSiteTests (3 tests) — RemoveMemberAsync + TransferOwnershipAsync with duplicate-keyed members
• ApiKeyAdministrationServiceTests (+1 test) — two stored keys both verify true → first-match returned, no throw

[codecov]

Codecov Report

❌ Patch coverage is 72.22222% with 10 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...arga.Team.Blazor/Features/Team/TeamComponent.razor	0.00%	6 Missing ⚠️
Tharga.Team/ResilientMemberLookup.cs	88.88%	0 Missing and 2 partials ⚠️
...rga.Team.Blazor/Features/Team/TeamInviteView.razor	0.00%	1 Missing ⚠️
Tharga.Team/TeamServiceBase.cs	85.71%	0 Missing and 1 partial ⚠️

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