Add struct literals, generics, log/print stdlib registration, activate DB wiring

- Register print/println/log/print_err in TypeEnv::with_builtins() with polymorphic (Unknown) param type so any value type is accepted without spurious warnings
- Add StructLit expr to AST + parser (uppercase-IDENT { ... } syntax), BuildStruct bytecode instruction + Struct value to runtime
- Add type_params to FnDef AST node and TypeParam variant to TypeExpr; parser parses <T, E> generics; type checker treats TypeParam as Unknown (universal type)
- Rewrite interpreter to support user-defined function calls via call stack (Frame + return_ip); dispatch_builtin handles print/println/log/print_err/__build_list__
- Fix engram_activate_search to unwrap { results: [...] } response envelope from /search; use std::net for sync HTTP to avoid reqwest dependency
- Add run-file command to CLI for single-file execution without el.toml
- Fix worktree engram-crypto path dep

bin/el/Cargo.toml

@@ -21,4 +21,5 @@ el-build    = { workspace = true }
 el-test     = { workspace = true }
 clap        = { workspace = true }
 thiserror   = { workspace = true }
+serde_json  = { workspace = true }
 tokio       = { version = "1", features = ["rt", "rt-multi-thread", "macros"] }