refactor: rewrite client with dynamic metadata, remove iteration-based queries

- Rewrite client to use subxt dynamic queries (no compile-time codegen)
- Remove functions requiring storage iteration (no on-chain index):
  - get_farm_ids_by_twin, get_farms_by_twin
  - get_nodes_by_farm, get_nodes_by_twin
  - is_farmer, get_farmer_info
- Fix get_node_ids_by_farm to use correct storage name (NodesByFarmID)
- Update dependencies to latest versions
- Add example mainnet_test.rs
- Update readme with current API documentation

Author: despiegk

clients/tfchain-client-go/.gitignore

@@ -0,0 +1 @@
+tfwallet

clients/tfchain-client-go/tfwallet_build.sh

@@ -0,0 +1,28 @@
+#!/bin/bash
+set -e
+
+echo "Building tfwallet (optimized)..."
+
+# Build with maximum optimization flags
+# -s: omit symbol table
+# -w: omit DWARF debugging info
+# -trimpath: remove file system paths from binary
+CGO_ENABLED=0 go build \
+    -ldflags="-s -w" \
+    -trimpath \
+    -o tfwallet \
+    ./cmd/tfwallet
+
+SIZE=$(ls -lh tfwallet | awk '{print $5}')
+echo "Binary size: $SIZE"
+
+# Compress with UPX if available (Linux only - macOS has issues)
+if [[ "$OSTYPE" != "darwin"* ]] && command -v upx &> /dev/null; then
+    echo "Compressing with UPX (maximum compression)..."
+    upx --best --lzma tfwallet
+    SIZE=$(ls -lh tfwallet | awk '{print $5}')
+    echo "Compressed size: $SIZE"
+fi
+
+echo ""
+echo "Build complete: ./tfwallet"