docs: update plan and develop to match current implementation

- Update architecture diagram: dual-protocol forwarder (DNS + DoH)
- Update goals to reflect what's built
- Update tech stack (added reqwest, base64, thiserror)
- Update directory structure to match real file tree
- Mark M2 as fully done, M3 done with UDP/TCP tests pending
- Update DEVELOP.md quick start commands

DEVELOP.md

@@ -5,18 +5,17 @@
 ```bash
 # Prerequisites
 rustup show            # Rust 1.80+
-cargo install cargo-watch
 
-# Run locally
-cargo run -- --config config/default.toml
+# Run locally (DoH on :8800, DNS on :53530)
+cargo run
 
-# Run with auto-reload
-cargo watch -x run
+# Run with custom config
+cargo run -- --config path/to/config.toml
 
 # Run tests
 cargo test
 
-# Lint
+# Lint & format
 cargo clippy -- -D warnings
 cargo fmt --check
 ```
@@ -87,7 +86,7 @@ See [docs/plan.md](docs/plan.md) for the full project plan and milestone checkli
 |-----------|--------|
 | M1 — Core Forwarding | ✅ Done |
 | M2 — Multiple Upstreams & Config | ✅ Done |
-| M3 — Local DNS Listener | ✅ Done |
+| M3 — Local DNS Listener | ✅ Done (UDP/TCP integration tests pending) |
 | M4 — Caching | 🔲 Not started |
 | M5 — Observability | 🔲 Not started |
 | M6 — Blocking & Filtering | 🔲 Not started |