feat: trace chunks with co-appearance relationships

- New trace_ingest module: creates chunks for each face trace (time + bbox + ASR text)
- Computes pairwise time overlaps between traces -> co_appearances in metadata
- Worker auto-triggers after face trace store + Qdrant sync
- SearchFilters: chunk_type filter (sentence/cut/trace/visual)
- SearchFilters: co_appears_with_trace_id filter

src/core/chunk/mod.rs

@@ -1,9 +1,11 @@
 pub mod rule1_ingest;
 pub mod rule3_ingest;
 pub mod splitter;
+pub mod trace_ingest;
 pub mod types;
 
 pub use rule1_ingest::execute_rule1;
 pub use rule3_ingest::ingest_rule3;
+pub use trace_ingest::ingest_traces;
 pub use splitter::{AsrSegment, ChunkSplitter};
 pub use types::{Chunk, ChunkType};