insight-chat: add get_faces_in_photo agentic tool

The LLM had no path to see face_detections data — get_file_tags
returns user-applied tags, but a face that's been detected and bound
to a person via the embedding-cluster auto-bind path doesn't always
have a matching tag. The new tool joins face_detections with persons
by content_hash and returns bound names + bboxes, plus unidentified
faces (so smaller models can count people in the photo without
inferring from a visual description).

Gated on face_detections being non-empty via the same has_any_*
pattern as daily_summaries.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/bin/populate_knowledge.rs

@@ -14,6 +14,7 @@ use image_api::database::{
     SqliteInsightDao, SqliteKnowledgeDao, SqliteLocationHistoryDao, SqliteSearchHistoryDao,
     connect,
 };
+use image_api::faces::{FaceDao, SqliteFaceDao};
 use image_api::file_types::{IMAGE_EXTENSIONS, VIDEO_EXTENSIONS};
 use image_api::libraries::{self, Library};
 use image_api::tags::{SqliteTagDao, TagDao};
@@ -182,6 +183,8 @@ async fn main() -> anyhow::Result<()> {
         Arc::new(Mutex::new(Box::new(SqliteTagDao::default())));
     let knowledge_dao: Arc<Mutex<Box<dyn KnowledgeDao>>> =
         Arc::new(Mutex::new(Box::new(SqliteKnowledgeDao::new())));
+    let face_dao: Arc<Mutex<Box<dyn FaceDao>>> =
+        Arc::new(Mutex::new(Box::new(SqliteFaceDao::new())));
 
     // Pass the full library set so `resolve_full_path` probes every root,
     // even when --library restricts the walk. A rel_path shared across
@@ -199,6 +202,7 @@ async fn main() -> anyhow::Result<()> {
         search_dao,
         tag_dao,
         knowledge_dao,
+        face_dao,
         all_libs.clone(),
     );