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/sniffer/p0f.py

@@ -22,6 +22,8 @@ No external dependencies.
 
 from __future__ import annotations
 
+from decnet.telemetry import traced as _traced
+
 # ─── TTL → initial TTL bucket ───────────────────────────────────────────────
 
 # Common "hop 0" TTLs. Packets decrement TTL once per hop, so we round up
@@ -216,6 +218,7 @@ def _match_signature(
     return True
 
 
+@_traced("sniffer.p0f_guess_os")
 def guess_os(
     ttl: int,
     window: int,