feat(server)!: promote server-ng to the Apache Iggy server

[hubcio]

Maintaining two servers meant every protocol change, config knob
and test lane got built twice, and the vsr feature let the
replicated paths drop out of a default build silently. Every SDK
and CI lane already targets the VSR server, so the fork can go.

VSR is now unconditional: the feature is gone, classic TCP, QUIC
and WebSocket framing is deleted, and the integration harness
always spawns the VSR server with a 3-node default cluster. The
legacy server, its compat lane, bdd compose flavor and config
modules are removed, and server-ng takes over the server package,
the iggy-server binary, the configs tree and the systemd
sd-notify integration. The published Dockerfile gains the
license generation stage ASF requires.

Restart scenarios are pinned to one node because a 3-node
topology trips a pre-existing partitions-plane view-change stall,
proven present at the base commit and tracked separately. The
cutover is also the only free moment to rotate the JWT
key-derivation context, so it is renamed here before the string
re-freezes.

BREAKING CHANGE: the wire protocol changed, so older SDKs and
CLIs cannot connect. The --fresh and
--with-default-root-credentials flags are gone, leaving
--replica-id. The -p server-ng and --bin iggy-server-ng cargo
targets no longer exist, and the SDK crate no longer has a vsr
feature.

[codecov]

Codecov Report

❌ Patch coverage is 90.46971% with 140 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.98%. Comparing base (91672aa) to head (2666e5e).

Files with missing lines	Patch %	Lines
core/configs/src/common/validators.rs	64.24%	67 Missing and 2 partials ⚠️
core/configs/src/server_config/validators.rs	89.92%	30 Missing and 8 partials ⚠️
core/configs/src/common/displays.rs	91.20%	8 Missing ⚠️
core/configs/src/server_config/sharding.rs	95.62%	8 Missing ⚠️
core/sdk/src/tcp/tcp_client.rs	69.23%	7 Missing and 1 partial ⚠️
core/configs/src/server_config/server.rs	88.88%	3 Missing and 1 partial ⚠️
core/configs/src/server_config/quic.rs	96.90%	3 Missing ⚠️
core/configs/src/server_config/message_bus.rs	90.90%	1 Missing ⚠️
core/sdk/src/quic/quic_client.rs	66.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #3856      +/-   ##
============================================
+ Coverage     76.91%   81.98%   +5.06%     
- Complexity     1021     1296     +275     
============================================
  Files          1363     1199     -164     
  Lines        175833   159943   -15890     
  Branches     146279   129651   -16628     
============================================
- Hits         135243   131126    -4117     
+ Misses        36715    25248   -11467     
+ Partials       3875     3569     -306     

Components	Coverage Δ
Rust Core	83.21% <90.46%> (+7.12%)	⬆️
Java SDK	66.15% <ø> (+2.92%)	⬆️
C# SDK	60.75% <ø> (-14.92%)	⬇️
Python SDK	89.98% <ø> (ø)
PHP SDK	84.26% <ø> (ø)
Node SDK	96.25% <ø> (ø)
Go SDK	68.60% <ø> (ø)

Files with missing lines	Coverage Δ
core/binary_protocol/src/consensus/command.rs	100.00% <ø> (ø)
core/binary_protocol/src/framing.rs	94.72% <ø> (-1.06%)	⬇️
...nary_protocol/src/requests/users/login_register.rs	98.46% <ø> (-1.54%)	⬇️
...ocol/src/requests/users/login_register_with_pat.rs	100.00% <ø> (ø)
...ary_protocol/src/responses/users/login_register.rs	100.00% <ø> (ø)
core/common/src/error/eviction.rs	90.47% <ø> (+42.85%)	⬆️
.../common/src/traits/binary_impls/consumer_groups.rs	100.00% <ø> (ø)
core/common/src/traits/binary_impls/messages.rs	85.84% <ø> (-11.66%)	⬇️
core/common/src/traits/binary_impls/mod.rs	92.50% <ø> (-4.17%)	⬇️
.../src/traits/binary_impls/personal_access_tokens.rs	100.00% <ø> (ø)
... and 63 more

... and 345 files with indirect coverage changes

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