feat(csharp): migrate to VSR wire protocol

[lukaszzborek]

The .NET SDK previously spoke classic TCP framing, which the clustered
next-generation server does not understand. Classic framing is now
dropped entirely: the SDK speaks VSR framing only, so every connection
goes through the register handshake, with session lifetime tied to the
connection, request sequencing, bounded reply decoding, transient
replays, leader redirection over the cluster roster, and
assignment-based consumer groups.

The IIggyClient surface is unchanged. Partitioning moves client-side
(balanced and message-key, hash byte-compatible with the Rust SDK),
credentials are bounds-checked before framing, and a request written
without a server verdict surfaces as VsrRequestOutcomeUnknownException
rather than being silently replayed on a new session, since that would
bypass server-side deduplication.

[codecov]

Codecov Report

❌ Patch coverage is 72.70064% with 466 lines in your changes missing coverage. Please review.
✅ Project coverage is 75.51%. Comparing base (c272f21) to head (e427d88).

Files with missing lines	Patch %	Lines
...IggyClient/Implementations/TcpMessageStream.Vsr.cs	59.84%	171 Missing and 33 partials ⚠️
...SDK/IggyClient/Implementations/TcpMessageStream.cs	60.28%	49 Missing and 7 partials ⚠️
...lient/Implementations/TransientHttpRetryHandler.cs	5.55%	51 Missing ⚠️
...DK/IggyClient/Implementations/HttpMessageStream.cs	2.08%	47 Missing ⚠️
foreign/csharp/Iggy_SDK/Vsr/VsrOperation.cs	75.78%	28 Missing and 3 partials ⚠️
...gn/csharp/Iggy_SDK/Vsr/ConsumerGroupClientState.cs	86.30%	15 Missing and 5 partials ⚠️
.../Iggy_SDK/Publishers/BackgroundMessageProcessor.cs	24.00%	18 Missing and 1 partial ⚠️
...oreign/csharp/Iggy_SDK/Publishers/IggyPublisher.cs	0.00%	11 Missing and 1 partial ⚠️
foreign/csharp/Iggy_SDK/Utils/ServerAddress.cs	89.47%	2 Missing and 4 partials ⚠️
foreign/csharp/Iggy_SDK/Vsr/LoginRegister.cs	94.59%	2 Missing and 2 partials ⚠️
... and 10 more

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #3800      +/-   ##
============================================
- Coverage     76.58%   75.51%   -1.07%     
  Complexity     1046     1046              
============================================
  Files          1347     1363      +16     
  Lines        171013   172476    +1463     
  Branches     142367   142615     +248     
============================================
- Hits         130966   130250     -716     
- Misses        36225    38388    +2163     
- Partials       3822     3838      +16     

Components	Coverage Δ
Rust Core	75.76% <ø> (-0.02%)	⬇️
Java SDK	63.67% <ø> (ø)
C# SDK	50.16% <72.70%> (-22.12%)	⬇️
Python SDK	88.70% <ø> (ø)
PHP SDK	82.97% <ø> (ø)
Node SDK	96.37% <ø> (+0.09%)	⬆️
Go SDK	69.18% <ø> (ø)

Files with missing lines	Coverage Δ
...csharp/Iggy_SDK/Configuration/AutoLoginSettings.cs	100.00% <100.00%> (ø)
...p/Iggy_SDK/Configuration/IggyClientConfigurator.cs	100.00% <100.00%> (ø)
...n/csharp/Iggy_SDK/Consumers/IggyConsumer.Rented.cs	61.40% <100.00%> (-10.40%)	⬇️
...n/csharp/Iggy_SDK/Consumers/IggyConsumerBuilder.cs	50.33% <100.00%> (-29.67%)	⬇️
.../csharp/Iggy_SDK/Contracts/SendMessagesResponse.cs	100.00% <100.00%> (ø)
...y_SDK/Exceptions/IggyInvalidStatusCodeException.cs	100.00% <100.00%> (ø)
.../Iggy_SDK/Exceptions/VsrSessionEvictedException.cs	100.00% <100.00%> (ø)
...reign/csharp/Iggy_SDK/Factory/IggyClientFactory.cs	92.59% <100.00%> (-2.41%)	⬇️
foreign/csharp/Iggy_SDK/Mappers/BinaryMapper.cs	69.41% <100.00%> (-23.79%)	⬇️
...ign/csharp/Iggy_SDK/Publishers/IggyPublisherOfT.cs	100.00% <100.00%> (ø)
... and 23 more

... and 77 files with indirect coverage changes

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[hubcio]

please remove e2e-vsr and make e2e use iggy-server-ng - we're dropping support for iggy-server.