feat(faces): domain entities, ports & no-op analyzer

Phase 2 increment 2:
- domain: Face, Person, BoundingBox, DetectedFace (512-d embeddings).
- ports: FaceAnalyzerPort (detect + embed from raw bytes; decodes internally
  so the application layer stays image/ML-crate agnostic) and FaceRepository
  (user-scoped face/person persistence).
- DTOs: PersonDto, FaceBoxDto.
- NoopFaceAnalyzer — reports is_ready()==false and returns no faces, so the
  whole People pipeline compiles and runs inert until the operator wires a
  real ONNX-backed analyzer.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JW6ghFMDtnRYuYNzZhb47M

src/infrastructure/services/mod.rs

@@ -17,6 +17,7 @@ pub mod migration_blob_backend;
 pub mod migration_job;
 pub mod mock_email_sender;
 pub mod nextcloud_chunked_upload_service;
+pub mod noop_face_analyzer;
 pub mod oidc_service;
 pub mod password_hasher;
 pub mod path_resolver_service;

src/infrastructure/services/noop_face_analyzer.rs

@@ -0,0 +1,26 @@
+//! Default no-op face analyzer.
+//!
+//! Used when no ML model is configured: it reports `is_ready() == false` and
+//! returns no faces, so the whole People pipeline compiles and runs inert
+//! until a real ONNX-backed analyzer (provided by the operator) replaces it.
+
+use async_trait::async_trait;
+
+use crate::application::ports::face_ports::FaceAnalyzerPort;
+use crate::common::errors::DomainError;
+use crate::domain::entities::face::DetectedFace;
+
+/// Analyzer that never detects anything.
+#[derive(Debug, Default, Clone, Copy)]
+pub struct NoopFaceAnalyzer;
+
+#[async_trait]
+impl FaceAnalyzerPort for NoopFaceAnalyzer {
+    fn is_ready(&self) -> bool {
+        false
+    }
+
+    async fn analyze(&self, _image_bytes: &[u8]) -> Result<Vec<DetectedFace>, DomainError> {
+        Ok(Vec::new())
+    }
+}