feat(phase-bc): pass 5 — pgdbgen, postgres EventStore/PluginStore, plugin hub wiring, OTel stack, reconnect DB tier

- Generate Server/db/dbgen/{events,plugins}.sql.go and full Server/db/pgdbgen/ (//go:build postgres gated)
- Implement PostgresStore EventStore and PluginStore methods in store/postgres.go
- Wire plugin host_events.go EventSink into hub broadcast path (SetPluginEventSink)
- Wire host_commands.go slash-command dispatcher: chat_command V1 handler + hub.SetPluginRegistry
- Add handlers_command.go + handlers_command_test.go for plugin slash-command dispatch
- Add reconnect_db_test.go: TestReconnect_BufferMiss_FallsBackToDBTier (cold-tier DB replay)
- Add otel-up/otel-down Makefile targets; docker-compose.otel.yml + prometheus.dev.yml
- Update PHASE_BC_LOCAL_TODO.md: mark in-session items complete; document remaining network-blocked steps
- Minor fixes: channel_handler access-control, router plugin handler wiring, service span instrumentation

Server/Makefile

@@ -4,10 +4,12 @@
 #                engines defined in sqlc.yaml (db/dbgen + db/pgdbgen).
 # sqlc-verify    Fail if either committed dbgen output is stale (used by CI).
 # sqlc-install   Install the pinned sqlc version into $GOBIN.
+# otel-up        Start Jaeger + Prometheus for local tracing development.
+# otel-down      Stop and remove the OTel dev containers.
 
 SQLC_VERSION := $(shell cat sqlc.version)
 
-.PHONY: sqlc-install sqlc-generate sqlc-verify
+.PHONY: sqlc-install sqlc-generate sqlc-verify otel-up otel-down
 
 sqlc-install:
 	go install github.com/sqlc-dev/sqlc/cmd/sqlc@$(SQLC_VERSION)
@@ -21,3 +23,14 @@ sqlc-verify:
 		echo "ERROR: generated sqlc output is stale. Run 'make sqlc-generate' and commit the result." ; \
 		exit 1 ; \
 	)
+
+# Phase B Step 8 — local OTel development stack.
+# Starts Jaeger (traces) and Prometheus (metrics) in Docker.
+# Jaeger UI:      http://localhost:16686
+# Prometheus UI:  http://localhost:9090
+# Run the server with: go build -tags otel . && ./owncord-server
+otel-up:
+	docker compose -f docker-compose.otel.yml up -d
+
+otel-down:
+	docker compose -f docker-compose.otel.yml down