feat: generator-emitted DTO constructor lambdas for IL trimming

[keithdv]

Summary

• Source generator discovers plain DTO return types from factory method signatures and emits DtoConstructorRegistry.Register<T>(() => new T()) calls
• [DynamicallyAccessedMembers(All)] on Register<T> preserves the entire type from IL trimming
• NeatooJsonTypeInfoResolver uses the registry instead of Activator.CreateInstance (which fails under trimming)
• Fixes DTO deserialization in trimmed Blazor WASM apps where IsTrimmable=true on domain assemblies causes DefaultJsonTypeInfoResolver's reflection-based discovery to fail

Closes #48

Why this is needed

Normal Blazor WASM apps don't hit this because their assemblies aren't trimmed (TrimMode=partial only trims IsTrimmable=true assemblies). RemoteFactory intentionally marks domain assemblies trimmable to remove server-only business logic from the client — a core value proposition. This means DefaultJsonTypeInfoResolver's reflection breaks for plain DTOs.

Verified

• All 2,068 tests pass (net9.0 + net10.0)
• Manual Blazor WASM verification: Published Design.Server in Release/net10.0, loaded in browser, clicked "Get All Items" and "Get Item fix: trimming-safe factory registration for all factory types #42" — ExampleDto deserialized with correct Id and Name values under IL trimming

Test plan

• All unit tests pass (490 x2 frameworks)
• All integration tests pass (502 x2 frameworks)
• All Design tests pass (42 x2 frameworks)
• Manual: trimmed Blazor WASM DTO deserialization works (collection + single item)
• Records not affected (ExampleRecordResult excluded from registry)
• Neatoo types not affected (still use DI-based CreateObject)

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