build(scripts): add per-artifact build scripts staging into dist/

One script per main artifact, all staging into dist/ (overridable via
--dist or VOICECAT_DIST_DIR):

- build-server.sh        server-release preset -> dist/server/
- build-windows-client.sh  windows-client DLL + dotnet publish -> dist/windows-client/
- build-macos-client.sh    XCFramework + xcodebuild VoiceCatMac.app -> dist/macos-client/
- build-libs.sh           libvoicecat per platform -> dist/lib/{macos,ios*,windows}/
                         + dist/lib/VoiceCatCore.xcframework/
- build-all.sh            orchestrator (host-applicable artifacts only)
- common.sh               shared helpers: dist/VCPKG_ROOT resolution, platform
                         guards, logging, --help from header comments

Host-platform guards prevent running the wrong script on the wrong OS.
build-libs.sh and build-macos-client.sh drive the existing validated
clients/apple/scripts/build-xcframework.sh rather than duplicating it.
dist/ added to .gitignore.

scripts/build-all.sh

@@ -0,0 +1,71 @@
+#!/usr/bin/env bash
+#
+# build-all.sh — build every artifact this host can produce and stage it under
+# dist/. Convenience wrapper over the per-artifact scripts in scripts/.
+#
+# On macOS:   server + libs (macOS slice + xcframework) + macos-client (.app)
+# On Windows: server + libs (windows DLL) + windows-client (.exe folder)
+# On Linux:   server only (no native client presets target Linux)
+#
+# Usage:
+#   scripts/build-all.sh                  # build everything host can, into ./dist
+#   scripts/build-all.sh --dist /out
+#   scripts/build-all.sh --no-configure   # passed through to each step
+#   scripts/build-all.sh --skip-client    # skip the GUI client(s)
+#   scripts/build-all.sh --skip-libs      # skip the library artifacts
+#   scripts/build-all.sh --skip-server    # skip the server
+#   scripts/build-all.sh -h|--help
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+VC_SCRIPT_NAME="build-all"
+source "$SCRIPT_DIR/common.sh"
+
+PASS_ARGS=()
+SKIP_CLIENT=false
+SKIP_LIBS=false
+SKIP_SERVER=false
+while [[ $# -gt 0 ]]; do
+    case "$1" in
+        --dist)         PASS_ARGS+=( --dist "$2" ); vc_set_dist "$2"; shift 2 ;;
+        --no-configure) PASS_ARGS+=( --no-configure ); shift ;;
+        --skip-client)  SKIP_CLIENT=true; shift ;;
+        --skip-libs)    SKIP_LIBS=true; shift ;;
+        --skip-server)  SKIP_SERVER=true; shift ;;
+        -h|--help)      vc_print_help "$0"; exit 0 ;;
+        *) vc_die "unknown arg: $1 (try --help)" ;;
+    esac
+done
+
+HOST="$(vc_host_os)"
+vc_log "host: $HOST   dist: $VC_DIST_DIR"
+
+run() {
+    local name="$1"; shift
+    vc_step "→ $name $*"
+    "$SCRIPT_DIR/$name" "$@" "${PASS_ARGS[@]}"
+}
+
+if ! $SKIP_SERVER; then
+    run build-server.sh
+fi
+
+if ! $SKIP_LIBS; then
+    if [[ "$HOST" == "macos" ]]; then
+        run build-libs.sh --platform macos
+    elif [[ "$HOST" == "windows" ]]; then
+        run build-libs.sh --platform windows
+    fi
+fi
+
+if ! $SKIP_CLIENT; then
+    if [[ "$HOST" == "macos" ]]; then
+        run build-macos-client.sh
+    elif [[ "$HOST" == "windows" ]]; then
+        run build-windows-client.sh
+    fi
+fi
+
+vc_ok "all done -> $VC_DIST_DIR"
+vc_log "contents:"
+( cd "$VC_DIST_DIR" && find . -maxdepth 3 | sort | sed 's/^/    /' ) || true