feat: real EXIF extraction via adapters-exif crate

- MetadataExtractorPort in domain (bytes → StructuredData)
- adapters-exif: NomExifExtractor using nom-exif, handles EXIF + TrackInfo
- Worker's MetadataExtractorPlugin delegates to port, no longer knows nom-exif
- Filters noisy binary tags (U8Array, Undefined, Unknown)

Cargo.toml

@@ -10,6 +10,7 @@ members = [
     "crates/adapters/event-payload",
     "crates/adapters/event-transport",
     "crates/adapters/nats",
+    "crates/adapters/exif",
     "crates/presentation",
     "crates/bootstrap",
     "crates/worker",
@@ -46,6 +47,7 @@ adapters-storage = { path = "crates/adapters/storage" }
 event-payload    = { path = "crates/adapters/event-payload" }
 event-transport  = { path = "crates/adapters/event-transport" }
 adapters-nats    = { path = "crates/adapters/nats" }
+adapters-exif    = { path = "crates/adapters/exif" }
 async-nats       = "0.48"
 async-stream     = "0.3"
 presentation  = { path = "crates/presentation" }