fix: skip binary download if already installed, symlink from existing path

Resolves bootstrapping deadlock where downloading sslocal requires internet
access via the very proxy being deployed. Also handles distros (Arch) where
shadowsocks-rust is installed via package manager to /usr/bin instead of
/usr/local/bin.

Priority:
  1. /usr/local/bin/sslocal exists → skip download
  2. sslocal found in PATH elsewhere → symlink to /usr/local/bin/sslocal
  3. not found → download from GitHub releases

Same logic applied to ssserver-rust in server/deploy.sh.
Also: stop conflicting shadowsocks.service before starting shadowsocks-client,
and detect pacman vs apt for privoxy install.

services/shadowsocks/client/deploy.sh

@@ -12,24 +12,42 @@ source "$ENV_FILE"
 
 require_env SS_SERVER SS_PORT SS_PASSWORD SS_METHOD
 
+SSLOCAL_BIN="/usr/local/bin/sslocal"
+
+# Install sslocal — skip download if already present, symlink if installed elsewhere
+if [[ -x "$SSLOCAL_BIN" ]]; then
+    log_info "sslocal already at $SSLOCAL_BIN ($($SSLOCAL_BIN --version 2>&1 | head -1)), skipping download"
+elif command -v sslocal &>/dev/null; then
+    existing="$(command -v sslocal)"
+    log_info "sslocal found at $existing, symlinking to $SSLOCAL_BIN"
+    ln -sf "$existing" "$SSLOCAL_BIN"
+else
     log_info "Downloading shadowsocks-rust client..."
     VERSION=$(curl -s https://api.github.com/repos/shadowsocks/shadowsocks-rust/releases/latest \
         | python3 -c "import sys,json; print(json.load(sys.stdin)['tag_name'])")
     ARCHIVE="shadowsocks-${VERSION}.x86_64-unknown-linux-gnu.tar.xz"
     wget -q "https://github.com/shadowsocks/shadowsocks-rust/releases/download/${VERSION}/${ARCHIVE}"
     tar -xf "$ARCHIVE"
-cp sslocal /usr/local/bin/sslocal
+    cp sslocal "$SSLOCAL_BIN"
-chmod +x /usr/local/bin/sslocal
+    chmod +x "$SSLOCAL_BIN"
     rm -f "$ARCHIVE" ssserver sslocal ssurl ssmanager redir tunnel
+fi
 
 log_info "Installing privoxy..."
+if command -v pacman &>/dev/null; then
+    pacman -S --noconfirm --needed privoxy
+else
     apt-get install -y privoxy
+fi
 
 log_info "Deploying configs..."
 mkdir -p /etc/shadowsocks-rust
 envsubst < "${INFRA_DIR}/config.json.example" > /etc/shadowsocks-rust/client.json
 cp "${INFRA_DIR}/privoxy.conf.example" /etc/privoxy/config
 
+log_info "Stopping any existing shadowsocks service on port 1080..."
+systemctl stop shadowsocks 2>/dev/null || true
+
 log_info "Installing service..."
 cp "${INFRA_DIR}/shadowsocks-client.service" /etc/systemd/system/
 systemctl daemon-reload

services/shadowsocks/server/deploy.sh

@@ -12,15 +12,25 @@ source "$ENV_FILE"
 
 require_env SS_PORT SS_PASSWORD SS_METHOD
 
+SSSERVER_BIN="/usr/local/bin/ssserver-rust"
+
+if [[ -x "$SSSERVER_BIN" ]]; then
+    log_info "ssserver-rust already at $SSSERVER_BIN ($($SSSERVER_BIN --version 2>&1 | head -1)), skipping download"
+elif command -v ssserver &>/dev/null; then
+    existing="$(command -v ssserver)"
+    log_info "ssserver found at $existing, symlinking to $SSSERVER_BIN"
+    ln -sf "$existing" "$SSSERVER_BIN"
+else
     log_info "Downloading shadowsocks-rust..."
     VERSION=$(curl -s https://api.github.com/repos/shadowsocks/shadowsocks-rust/releases/latest \
         | python3 -c "import sys,json; print(json.load(sys.stdin)['tag_name'])")
     ARCHIVE="shadowsocks-${VERSION}.x86_64-unknown-linux-gnu.tar.xz"
     wget -q "https://github.com/shadowsocks/shadowsocks-rust/releases/download/${VERSION}/${ARCHIVE}"
     tar -xf "$ARCHIVE"
-cp ssserver /usr/local/bin/ssserver-rust
+    cp ssserver "$SSSERVER_BIN"
-chmod +x /usr/local/bin/ssserver-rust
+    chmod +x "$SSSERVER_BIN"
     rm -f "$ARCHIVE" ssserver sslocal ssurl ssmanager redir tunnel
+fi
 
 log_info "Deploying config..."
 mkdir -p /etc/shadowsocks-rust