feat: port session 04 — Logging, Signals & Services

- NatsLogger.cs: INatsLogger interface (Noticef/Warnf/Fatalf/Errorf/Debugf/Tracef),
  ServerLogging state class with atomic debug/trace flags, rate-limited logging
  (RateLimitWarnf/RateLimitDebugf), error variants (Errors/Errorc/Errorsc),
  MicrosoftLoggerAdapter bridging to ILogger
- SignalHandler.cs: ProcessSignal (Unix kill via Process), CommandToUnixSignal mapping
  (Stop→SIGKILL, Quit→SIGINT, Reopen→SIGUSR1, Reload→SIGHUP), ResolvePids via pgrep,
  SetProcessName, Run/IsWindowsService stubs for non-Windows
- 11 tests (6 logger, 5 signal/service)
- WASM/Windows signal stubs already n/a
- All 141 tests pass (140 unit + 1 integration)
- DB: features 368/3673 complete, tests 155/3257 complete (9.6% overall)

reports/current.md

@@ -1,6 +1,6 @@
 # NATS .NET Porting Status Report
 
-Generated: 2026-02-26 16:51:01 UTC
+Generated: 2026-02-26 16:54:25 UTC
 
 ## Modules (12 total)
 
@@ -13,19 +13,19 @@ Generated: 2026-02-26 16:51:01 UTC
 
 | Status | Count |
 |--------|-------|
-| complete | 344 |
+| complete | 368 |
 | n_a | 82 |
-| not_started | 3180 |
-| stub | 67 |
+| not_started | 3155 |
+| stub | 68 |
 
 ## Unit Tests (3257 total)
 
 | Status | Count |
 |--------|-------|
-| complete | 148 |
-| n_a | 49 |
-| not_started | 2980 |
-| stub | 80 |
+| complete | 155 |
+| n_a | 50 |
+| not_started | 2953 |
+| stub | 99 |
 
 ## Library Mappings (36 total)
 
@@ -36,4 +36,4 @@ Generated: 2026-02-26 16:51:01 UTC
 
 ## Overall Progress
 
-**634/6942 items complete (9.1%)**
+**666/6942 items complete (9.6%)**