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/db/models.py

@@ -43,6 +43,11 @@ class Log(SQLModel, table=True):
     raw_line: str = Field(sa_column=Column("raw_line", Text, nullable=False))
     fields: str = Field(sa_column=Column("fields", Text, nullable=False))
     msg: Optional[str] = Field(default=None, sa_column=Column("msg", Text, nullable=True))
+    # OTEL trace context — bridges the collector→ingester trace to the SSE
+    # read path.  Nullable so pre-existing rows and non-traced deployments
+    # are unaffected.
+    trace_id: Optional[str] = Field(default=None)
+    span_id: Optional[str] = Field(default=None)
 
 class Bounty(SQLModel, table=True):
     __tablename__ = "bounty"