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/auth/api_login.py

@@ -3,6 +3,7 @@ from typing import Any, Optional
 
 from fastapi import APIRouter, HTTPException, status
 
+from decnet.telemetry import traced as _traced
 from decnet.web.auth import (
     ACCESS_TOKEN_EXPIRE_MINUTES,
     create_access_token,
@@ -24,6 +25,7 @@ router = APIRouter()
         422: {"description": "Validation error"}
     },
 )
+@_traced("api.login")
 async def login(request: LoginRequest) -> dict[str, Any]:
     _user: Optional[dict[str, Any]] = await repo.get_user_by_username(request.username)
     if not _user or not verify_password(request.password, _user["password_hash"]):