feat(server-ng): harden listener, auth, shutdown, and disk-poll paths

[numinnex]

Silent failure modes become loud or typed: listeners no longer set
SO_REUSEPORT, so a stale process holding a port fails the bind instead
of splitting the accept queue (UDP/QUIC drops SO_REUSEADDR too, which
alone lets a second socket steal datagrams); a disk poll that cannot
resolve its partition dir mid-rotation now fails closed instead of
letting the journal-forward skip disk-resident offsets; rejected logins
get a typed Eviction frame with the real reason instead of an empty
reply; a wedged shard is abandoned at a configurable join deadline
instead of blocking process exit forever.

Cluster operability: a verify-only acceptance window for the retiring
PSK (cluster.auth.previous_shared_secret) makes key rotation a rolling
three-step instead of a coordinated restart, and replica TLS names are
keyed by replica id rather than roster position so sparse ids from
dynamic join cannot verify against another peer's name.

Also removes a stale rustdoc pointer to the already-landed resumable
TLS pump framing.

[codecov]

Codecov Report

❌ Patch coverage is 69.35484% with 95 lines in your changes missing coverage. Please review.
✅ Project coverage is 61.15%. Comparing base (0fa657a) to head (29a2678).

Files with missing lines	Patch %	Lines
core/server-ng/src/bootstrap.rs	0.00%	56 Missing ⚠️
core/partitions/src/iggy_partition.rs	71.69%	13 Missing and 2 partials ⚠️
core/server-ng/src/auth.rs	76.47%	8 Missing ⚠️
core/server-ng/src/dispatch.rs	0.00%	8 Missing ⚠️
core/server-ng/src/server_error.rs	0.00%	7 Missing ⚠️
core/partitions/src/poll_plan.rs	83.33%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             master    #3774       +/-   ##
=============================================
- Coverage     75.12%   61.15%   -13.97%     
  Complexity      969      969               
=============================================
  Files          1307     1306        -1     
  Lines        152751   140486    -12265     
  Branches     128184   115991    -12193     
=============================================
- Hits         114756    85920    -28836     
- Misses        34465    50964    +16499     
- Partials       3530     3602       +72     

Components	Coverage Δ
Rust Core	58.55% <69.35%> (-16.99%)	⬇️
Java SDK	62.71% <ø> (ø)
C# SDK	71.13% <ø> (-1.14%)	⬇️
Python SDK	92.27% <ø> (ø)
PHP SDK	84.52% <ø> (ø)
Node SDK	92.20% <ø> (-0.05%)	⬇️
Go SDK	43.08% <ø> (ø)

Files with missing lines	Coverage Δ
core/configs/src/server_ng_config/cluster.rs	97.73% <100.00%> (+0.08%)	⬆️
core/configs/src/server_ng_config/sharding.rs	95.81% <100.00%> (+1.21%)	⬆️
core/message_bus/src/client_listener/mod.rs	73.07% <ø> (ø)
core/message_bus/src/client_listener/quic.rs	78.43% <ø> (+1.23%)	⬆️
core/message_bus/src/framing.rs	78.31% <ø> (ø)
core/message_bus/src/installer/replica.rs	85.97% <100.00%> (ø)
core/message_bus/src/replica/auth.rs	95.70% <100.00%> (+1.14%)	⬆️
core/message_bus/src/replica/handshake.rs	79.25% <ø> (ø)
core/message_bus/src/socket_opts.rs	91.30% <100.00%> (+8.95%)	⬆️
core/partitions/src/poll_plan.rs	64.45% <83.33%> (+0.69%)	⬆️
... and 5 more

... and 265 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.