feat: async dish recognition (Kafka/Watermill/SSE) + remove Wire + consolidate migrations

Async recognition pipeline:
- POST /ai/recognize-dish → 202 {job_id, queue_position, estimated_seconds}
- GET /ai/jobs/{id}/stream — SSE stream: queued → processing → done/failed
- Kafka topics: ai.recognize.paid (3 partitions) + ai.recognize.free (1 partition)
- 5-worker WorkerPool with priority loop (paid consumers first)
- SSEBroker via PostgreSQL LISTEN/NOTIFY
- Kafka adapter migrated from franz-go to Watermill (watermill-kafka/v2)
- Docker Compose: added Kafka + Zookeeper + kafka-init service
- Flutter: recognition_service.dart uses SSE; home_screen shows live job status

Remove google/wire (archived):
- Deleted wire.go (wireinject spec) and wire_gen.go
- Added cmd/server/init.go — plain Go manual DI, same initApp() logic
- Removed github.com/google/wire from go.mod

Consolidate migrations:
- Merged 001_initial_schema + 002_seed_data + 003_recognition_jobs into single 001_initial_schema.sql
- Deleted 002_seed_data.sql and 003_recognition_jobs.sql

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/go.mod

@@ -4,6 +4,8 @@ go 1.25.5
 
 require (
 	firebase.google.com/go/v4 v4.19.0
+	github.com/ThreeDotsLabs/watermill v1.5.1
+	github.com/ThreeDotsLabs/watermill-kafka/v2 v2.5.0
 	github.com/go-chi/chi/v5 v5.2.5
 	github.com/go-chi/cors v1.2.2
 	github.com/golang-jwt/jwt/v5 v5.3.1
@@ -33,6 +35,7 @@ require (
 	github.com/GoogleCloudPlatform/opentelemetry-operations-go/internal/resourcemapping v0.53.0 // indirect
 	github.com/MicahParks/keyfunc v1.9.0 // indirect
 	github.com/Microsoft/go-winio v0.6.2 // indirect
+	github.com/Shopify/sarama v1.38.0 // indirect
 	github.com/cenkalti/backoff/v4 v4.3.0 // indirect
 	github.com/cespare/xxhash/v2 v2.3.0 // indirect
 	github.com/cncf/xds/go v0.0.0-20251022180443-0feb69152e9f // indirect
@@ -46,6 +49,9 @@ require (
 	github.com/docker/docker v28.5.1+incompatible // indirect
 	github.com/docker/go-connections v0.6.0 // indirect
 	github.com/docker/go-units v0.5.0 // indirect
+	github.com/eapache/go-resiliency v1.3.0 // indirect
+	github.com/eapache/go-xerial-snappy v0.0.0-20180814174437-776d5712da21 // indirect
+	github.com/eapache/queue v1.1.0 // indirect
 	github.com/ebitengine/purego v0.8.4 // indirect
 	github.com/envoyproxy/go-control-plane/envoy v1.35.0 // indirect
 	github.com/envoyproxy/protoc-gen-validate v1.2.1 // indirect
@@ -56,15 +62,24 @@ require (
 	github.com/go-ole/go-ole v1.2.6 // indirect
 	github.com/golang-jwt/jwt/v4 v4.5.2 // indirect
 	github.com/golang/protobuf v1.5.4 // indirect
+	github.com/golang/snappy v0.0.4 // indirect
 	github.com/google/s2a-go v0.1.9 // indirect
-	github.com/google/wire v0.7.0 // indirect
 	github.com/googleapis/enterprise-certificate-proxy v0.3.11 // indirect
 	github.com/googleapis/gax-go/v2 v2.17.0 // indirect
 	github.com/grpc-ecosystem/grpc-gateway/v2 v2.27.8 // indirect
+	github.com/hashicorp/errwrap v1.1.0 // indirect
+	github.com/hashicorp/go-multierror v1.1.1 // indirect
+	github.com/hashicorp/go-uuid v1.0.3 // indirect
 	github.com/jackc/pgpassfile v1.0.0 // indirect
 	github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 // indirect
 	github.com/jackc/puddle/v2 v2.2.2 // indirect
-	github.com/klauspost/compress v1.18.0 // indirect
+	github.com/jcmturner/aescts/v2 v2.0.0 // indirect
+	github.com/jcmturner/dnsutils/v2 v2.0.0 // indirect
+	github.com/jcmturner/gofork v1.7.6 // indirect
+	github.com/jcmturner/gokrb5/v8 v8.4.3 // indirect
+	github.com/jcmturner/rpc/v2 v2.0.3 // indirect
+	github.com/klauspost/compress v1.18.4 // indirect
+	github.com/lithammer/shortuuid/v3 v3.0.7 // indirect
 	github.com/lufia/plan9stats v0.0.0-20211012122336-39d0f177ccd0 // indirect
 	github.com/magiconair/properties v1.8.10 // indirect
 	github.com/mfridman/interpolate v0.0.2 // indirect
@@ -76,12 +91,15 @@ require (
 	github.com/moby/sys/userns v0.1.0 // indirect
 	github.com/moby/term v0.5.0 // indirect
 	github.com/morikuni/aec v1.0.0 // indirect
+	github.com/oklog/ulid v1.3.1 // indirect
 	github.com/opencontainers/go-digest v1.0.0 // indirect
 	github.com/opencontainers/image-spec v1.1.1 // indirect
+	github.com/pierrec/lz4/v4 v4.1.25 // indirect
 	github.com/pkg/errors v0.9.1 // indirect
 	github.com/planetscale/vtprotobuf v0.6.1-0.20240319094008-0393e58bdf10 // indirect
 	github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 // indirect
 	github.com/power-devops/perfstat v0.0.0-20210106213030-5aafc221ea8c // indirect
+	github.com/rcrowley/go-metrics v0.0.0-20201227073835-cf1acfcdf475 // indirect
 	github.com/sethvargo/go-retry v0.3.0 // indirect
 	github.com/shirou/gopsutil/v4 v4.25.6 // indirect
 	github.com/sirupsen/logrus v1.9.3 // indirect
@@ -92,6 +110,7 @@ require (
 	github.com/yusufpapurcu/wmi v1.2.4 // indirect
 	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
 	go.opentelemetry.io/contrib/detectors/gcp v1.38.0 // indirect
+	go.opentelemetry.io/contrib/instrumentation/github.com/Shopify/sarama/otelsarama v0.31.0 // indirect
 	go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.61.0 // indirect
 	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.61.0 // indirect
 	go.opentelemetry.io/otel v1.40.0 // indirect
@@ -102,11 +121,11 @@ require (
 	go.opentelemetry.io/otel/trace v1.40.0 // indirect
 	go.opentelemetry.io/proto/otlp v1.9.0 // indirect
 	go.uber.org/multierr v1.11.0 // indirect
-	golang.org/x/crypto v0.47.0 // indirect
+	golang.org/x/crypto v0.48.0 // indirect
 	golang.org/x/net v0.49.0 // indirect
 	golang.org/x/oauth2 v0.35.0 // indirect
 	golang.org/x/sync v0.19.0 // indirect
-	golang.org/x/sys v0.40.0 // indirect
+	golang.org/x/sys v0.41.0 // indirect
 	golang.org/x/text v0.34.0 // indirect
 	golang.org/x/time v0.14.0 // indirect
 	google.golang.org/appengine/v2 v2.0.6 // indirect