docs: tambah doc comment, logging, dan inline comments di semua 255 file

Meliputi:
- File-level //! doc comment: tujuan file, alur kerja, komponen utama
- Function-level /// doc comment: apa, parameter, return, flow, edge cases
- Struct/enum/trait /// doc comment: peran, field docs
- Tracing logging (tracing::info!/debug!/trace!/warn!/error!) di setiap fungsi
- Inline comments untuk variable dan branching logic penting
- Seluruh 8 crates di workspace: zesdex-backend, zesdex-cms, zesdex-entities,
  zesdex-iam, zesdex-infra, zesdex-ipc, zesdex-middleware, zesdex-utils
- Build: 0 errors, 242/242 tests passed

crates/zesdex-backend/src/app/runtime/stream/mod.rs

@@ -1,6 +1,15 @@
 //! SSE stream parser: converts SSE- or JSON-chunked LLM responses into
 //! typed `StreamEvent` variants (tokens, reasoning, tool calls, usage, done).
+
+/// JSON-repair utilities for malformed streaming fragments (truncated JSON,
+/// missing brackets, escaped newlines inside strings).
 pub mod json_repair;
+
+/// Turn-level streaming state machine: manages buffering, SSE parsing,
+/// tool-call accumulation, and per-chunk event dispatch.
 pub mod turn;
 
+/// Re-export from `zesdex-entities` for convenience:
+/// - `SseParser` — low-level SSE line/event parser
+/// - `StreamEvent` — typed event variants yielded by the parser
 pub use zesdex_entities::{SseParser, StreamEvent};