refactor: remove bal-pusher-enhanced and update docs/env

- Remove src/bin/bal-pusher-enhanced.rs (synchronous pusher variant)
- Remove bal-pusher.env and bal-pusher.sh from git tracking (now in .gitignore)
- Update all documentation to remove references to bal-pusher-enhanced:
  * 01_project_overview.md
  * 02_glossary_and_bitcoin_domain.md
  * 03_architecture_and_data_flow.md
  * 04_modules_detail.md
  * 05_api_reference.md (remove rawblock ZMQ section, update references)
  * 08_security_audit.md (remove references to bal-pusher-enhanced in DoS and ZMQ sections)
  * 09_references_and_links.md
- Build verified: cargo check passes for bal-pusher and bal-server binaries

docs/01_project_overview.md

@@ -21,7 +21,6 @@ The project consists of three primary binaries and two shared libraries:
 
 1. **`bal-server`**: Async HTTP server (hyper + tokio) that exposes the API for receiving transactions and serving statistics.
 2. **`bal-pusher`**: Async daemon that listens for `hashblock` ZMQ messages and pushes pending transactions to a Bitcoin node via RPC.
-3. **`bal-pusher-enhanced`**: Synchronous variant of the pusher that listens for `rawblock` ZMQ messages and computes the block median time from the raw header without RPC calls.
 4. **`lib.rs`**: Exports the shared modules `db` and `xpub`.
 5. **`db.rs`**: All database operations and schema creation for SQLite `0.34.0`.
 6. **`xpub.rs`**: Address derivation from xpub/zpub using BIP-84 and the `bitcoin` crate.