feat: implement full pipeline (pgvector, embeddings, ingest, query, HTTP)

- Add database schema with pgvector extension (L0/L1/L2 memories)
- Implement pgvector-backed vector store with similarity search
- Add Ollama embeddings client for 768-dim nomic embeddings
- Implement ingest worker to process records into L0/L1 memory
- Implement query worker with semantic search across memory tiers
- Rewrite HTTP server with database connection pooling
- Wire all endpoints to actual backend (ingest, query, projects, skills)
- Update main.rs to use DATABASE_URL from environment
- All code compiles, ready for Docker build and deployment

Cargo.toml

@@ -38,6 +38,9 @@ once_cell = "1.19"
 actix-web = "4.4"
 actix-rt = "2.9"
 uuid = { version = "1.6", features = ["v4", "serde"] }
+sqlx = { version = "0.7", features = ["postgres", "runtime-tokio-rustls", "chrono", "uuid", "json"] }
+pgvector = { version = "0.2", features = ["sqlx"] }
+base64 = "0.21"
 
 [dev-dependencies]
 toml = { workspace = true }