feat: complete OTEL tracing across all services with pipeline bridge and docs

Extends tracing to every remaining module: all 23 API route handlers,
correlation engine, sniffer (fingerprint/p0f/syslog), prober (jarm/hassh/tcpfp),
profiler behavioral analysis, logging subsystem, engine, and mutator.

Bridges the ingester→SSE trace gap by persisting trace_id/span_id columns on
the logs table and creating OTEL span links in the SSE endpoint. Adds log-trace
correlation via _TraceContextFilter injecting otel_trace_id into Python LogRecords.

Includes development/docs/TRACING.md with full span reference (76 spans),
pipeline propagation architecture, quick start guide, and troubleshooting.

decnet/prober/worker.py

@@ -169,6 +169,7 @@ def _write_event(
 
 # ─── Target discovery from log stream ────────────────────────────────────────
 
+@_traced("prober.discover_attackers")
 def _discover_attackers(json_path: Path, position: int) -> tuple[set[str], int]:
     """
     Read new JSON log lines from the given position and extract unique
@@ -399,6 +400,7 @@ def _tcpfp_phase(
 
 # ─── Main worker ─────────────────────────────────────────────────────────────
 
+@_traced("prober.worker")
 async def prober_worker(
     log_file: str,
     interval: int = 300,