Adds tests/unit/quic_socket_branch_test.cpp with 53 hermetic test cases
exercising public-API surfaces of src/internal/quic_socket.cpp that
remained uncovered after Issue #989. Targets the #953 acceptance bar of
line >= 70% / branch >= 60%.

Coverage includes: short-lived construction loops for both client and
server roles; default invariants for state, role, is_connected,
is_handshake_complete, remote_endpoint, remote_connection_id;
local_connection_id RFC 9000 length bounds and pairwise uniqueness
across 16 sockets; callback registration with default-constructed,
replaced, and shared_ptr-captured handlers for all four callback types;
mutable and const socket() accessor reachability; role-guard rejection
in connect/accept (server-cannot-connect with and without SNI,
client-cannot-accept with empty and missing PEM paths, repeated
rejection idempotency); close() idempotency on idle/draining/closed
including triple-close, application-error-code branch with max-uint64
and 1024-character reason; send_stream_data not-connected guard;
create_stream not-connected guard for client/server bidi/uni;
close_stream not_found early-return for nine unknown ids;
start_receive/stop_receive flag transitions; move construction and
move assignment with populated callbacks; self-move-assignment via
reference; concurrent state-query polling and concurrent callback
replacement under shared_ptr lifetime; multi-instance independent
state; destructor cleanup paths.

Honest scope: the impl-level methods that physically exchange QUIC
packets with a peer (do_receive, handle_packet, process_frame and
its dispatch branches, process_crypto_frame, process_stream_frame,
process_ack_frame, process_connection_close_frame,
process_handshake_done_frame, send_pending_packets populated path,
send_packet encryption + async_send_to dispatch, queue_crypto_data
populated state, determine_encryption_level per-packet-type dispatch,
on_retransmit_timeout) require a live UDP/QUIC peer and remain
uncovered without a transport fixture. The connect()/accept() success
paths past TLS init also need a peer or PEM files on disk.

Closes #1051
Part of #953

* test(quic): add branch coverage tests for quic_server.cpp

Add tests/unit/quic_server_branch_test.cpp complementing
experimental_quic_server_test.cpp (Issue #989). Covers public-API
surfaces of messaging_quic_server reachable without a live QUIC peer:

- quic_server_config full-field round-trips: empty/1024-char/binary-byte
  cert/key paths, optional ca_cert_file present and absent,
  require_client_cert toggling, ALPN protocol vector growth (empty,
  single, four-with-empty-string, 32-entry), all six numeric settings
  at zero and std::numeric_limits boundaries, enable_retry toggle,
  retry_key vector growth (empty, 16, 256 bytes), full-config copy
  round-trip preserving every field
- Construction with empty / 512-char / binary-byte server IDs,
  16-iteration short-lived loops, server_id() reference stability
- Default-state queries on a never-started server: is_running,
  session_count, connection_count, sessions, get_session
- stop_server() rejection branch when never started, repeated rejection
  idempotency, i_quic_server::stop() interface delegation
- disconnect_session() not_found branch for unknown/empty/long/binary
  ids and varied error codes
- disconnect_all() empty-map no-op for varied error codes
- broadcast() and multicast() empty-map ok-return for empty/small/64KiB
  payloads, repeated invocation, empty session_ids, many unknown ids
- Legacy callback registration with empty std::function / triple
  replacement / shared_ptr capture for all five callback types
- Interface (i_quic_server) callback adapters for all five callbacks
  with null callbacks, populated lambdas, triple replacement
- Concurrent polling of is_running / session_count / server_id /
  sessions and concurrent legacy callback replacement under shared_ptr
- Multi-instance independent default state across 8 servers
- Destructor on never-started, after failed-stop, with callbacks
  registered

The impl-level packet-driven paths (do_start_impl, do_stop_impl,
start_receive, handle_packet, find_or_create_session, on_session_close,
start_cleanup_timer, cleanup_dead_sessions, all five invoke_*_callback
helpers, populated-map broadcast/multicast/disconnect_session/
disconnect_all branches) require a live QUIC client that completes a
TLS handshake or a friend-declared injection point and remain
uncovered.

Register network_quic_server_branch_test in tests/CMakeLists.txt.
Update CHANGELOG.md and docs/CHANGELOG.md.

Closes #1052
Part of #953

* test(quic): rename namespace alias iface to qiface to avoid Linux net/if.h struct iface conflict

…1059)

Add tests/unit/websocket_server_branch_test.cpp exercising public-API
surfaces of messaging_ws_server that remained uncovered after Issue #989
baseline measurement (line 39.9% / branch 19.7%).

Coverage targets:
- ws_server_config full-field round-trip (port / max_connections /
  ping_interval / max_message_size at zero / 1 / max boundaries, path
  with empty / 1024-char / binary-byte values, auto_pong toggle)
- messaging_ws_server construction with empty / 512-char / binary-byte
  server IDs and string_view literal variant
- Default-state queries on never-started server (is_running,
  connection_count, get_connection, get_all_connections)
- stop_server() / i_websocket_server::stop() returning ok() on
  prepare_stop() early-return branch
- broadcast_text() / broadcast_binary() session_mgr_ == nullptr
  early-return for empty / small / 64 KiB payloads
- Interface (i_websocket_server) callback adapters for connection /
  disconnection / text / binary / error with null callbacks (empty-
  function branch), populated lambdas, triple replacement, shared_ptr-
  captured state, and null-then-populated-then-null toggle
- Concurrent state queries and callback replacement under shared_ptr
- Multi-instance independent state and type alias coverage
- Destructor cleanup paths

Tests are hermetic: no live TCP peer, no WebSocket handshake. The impl-
level methods that exchange frames remain reachable only with a
transport fixture; this PR documents them in an honest scope statement.

Closes #1053