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/web/router/logs/api_get_histogram.py

@@ -2,6 +2,7 @@ from typing import Any, Optional
 
 from fastapi import APIRouter, Depends, Query
 
+from decnet.telemetry import traced as _traced
 from decnet.web.dependencies import require_viewer, repo
 
 router = APIRouter()
@@ -9,6 +10,7 @@ router = APIRouter()
 
 @router.get("/logs/histogram", tags=["Logs"],
     responses={401: {"description": "Could not validate credentials"}, 422: {"description": "Validation error"}},)
+@_traced("api.get_logs_histogram")
 async def get_logs_histogram(
     search: Optional[str] = None,
     start_time: Optional[str] = Query(None),