Nuke Zcash from build infra (chain already disabled at config layer)

Removed:
- cw_zcash/ directory (Dart wrapper, no longer needed)
- assets/zcash_node_list.yml
- scripts/prepare_zcash.sh
- scripts/{android,ios,linux,macos}/build_zcash.sh
- scripts/android/docker/Dockerfile.zcash
- scripts/zcash_lib/ if cloned (rebuildable from prepare_zcash.sh which is also gone)

Edited:
- scripts/lint.sh: replaced cw_zcash loop target with the actual modules we
  ship (cw_core, cw_monero, cw_wownero, cw_bitcoin, cw_bitcoin_cash,
  cw_dogecoin, cw_evm, cw_nano).
- hashwallet.bat: trimmed mobx codegen loop to enabled chains.
- pubspec_base.yaml: dropped zcash_node_list.yml + zcash_lib sapling
  asset references.
- scripts/android/docker/{build.sh,Dockerfile.final}: removed zcash image
  build + COPY stage.

tool/configure.dart still has the zcash codegen functions intact (they
just don't fire because we don't pass --zcash); leaving them as harmless
dead code rather than risking a regression in the codegen pipeline.

assets/zcash_node_list.yml

@@ -1,12 +0,0 @@
-- uri: zec.rocks:443
-  is_default: false
-  useSSL: true
-  isEnabledForAutoSwitching: true
-- uri: zec-node.cakewallet.com:443
-  is_default: true
-  useSSL: true
-  isEnabledForAutoSwitching: true
-- uri: 2c4whzg26j6hgjh22rxynj3oig4gm22ga7x74weclujywxye23v3u5id.onion:9067
-  useSSL: false
-- uri: bvp2l442g5ogma7rywzahm7eqyhpp3g26n3gvvxeioqn5csio2ir6myd.onion:9067
-  useSSL: false