Add Selkies streamer prototype for Java games

Runs a Flashpoint game natively in a container and streams it to the
browser. fp-launch follows the Linux launcher's sequence: start the game
server, mount the game's zip, and run startJava.sh through the proxy.

streaming/streamer/Dockerfile

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+FROM ghcr.io/linuxserver/baseimage-selkies:debiantrixie
+
+RUN apt-get update && \
+  DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
+    fontconfig \
+    fonts-dejavu-core \
+    libasound2-plugins \
+    libxi6 \
+    libxrender1 \
+    libxtst6 \
+    sqlite3 && \
+  rm -rf /var/lib/apt/lists/*
+
+COPY root/ /

streaming/streamer/README.md

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+# Flashpoint streamer (prototype)
+
+Runs a Flashpoint game natively on the server and streams it to the browser with
+[Selkies](https://github.com/selkies-project/selkies), for platforms that cannot
+run in a browser. One container plays one game, set by `GAME_ID`. Only Java
+applets are supported so far.
+
+## Requirements
+
+A Linux Flashpoint install at `FLASHPOINT_HOST_PATH`. The streamer uses the
+Infinity build's `Server/FlashpointGameServer` and `FPSoftware/Java`, which
+Ultimate's packed zips do not include on Linux. To add them to an extracted
+Ultimate without overwriting its data, copy an extracted
+[Infinity for Linux](https://flashpointarchive.org/downloads) over it:
+
+```sh
+rsync -a --ignore-existing /path/to/infinity/ /path/to/flashpoint/
+```
+
+## Usage
+
+```sh
+FLASHPOINT_HOST_PATH=/path/to/flashpoint docker compose up -d --build
+```
+
+Open `https://<host>:3001` and accept the self-signed certificate. To play a
+different game, set `GAME_ID` and recreate the container. The launch log is at
+`/config/fp-launch.log` inside the container.
+
+## How it works
+
+`fp-launch` follows the Flashpoint launcher's Linux launch sequence: it starts
+the game server, mounts the game's zip through the server's `mountzip` API, and
+runs the game's application with its HTTP proxy pointed at the game server.
+Selkies restarts the game when it exits (`RESTART_APP`).

streaming/streamer/compose.yaml

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+services:
+  flashpoint-streamer:
+    build: .
+    container_name: flashpoint-streamer
+    shm_size: 1gb
+    ports:
+      - "${STREAMER_PORT:-3001}:3001"
+    volumes:
+      - ${FLASHPOINT_HOST_PATH:?FLASHPOINT_HOST_PATH is required}:/flashpoint:ro
+    environment:
+      - PUID=${PUID:-1000}
+      - PGID=${PGID:-1000}
+      - GAME_ID=${GAME_ID:-247a4c93-c252-49c8-8bc9-fb43d5c039df}
+      - RESTART_APP=true
+      - NO_DECOR=true
+      - TITLE=Flashpoint

streaming/streamer/root/defaults/autostart

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+fp-launch "$GAME_ID" >>"$HOME/fp-launch.log" 2>&1

streaming/streamer/root/etc/asound.conf

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+pcm.!default { type pulse }
+ctl.!default { type pulse }

streaming/streamer/root/usr/local/bin/fp-launch

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+#!/usr/bin/env bash
+# Launch a Flashpoint game by ID the way the Linux launcher does: start the
+# game server, mount the game's zip, then run its application through the proxy.
+set -euo pipefail
+
+FP_PATH=${FP_PATH:-/flashpoint}
+ID=${1:?usage: fp-launch <game id>}
+DB=$FP_PATH/Data/flashpoint.sqlite
+API=http://127.0.0.1:22501/fpProxy/api
+
+[[ $ID =~ ^[0-9a-f-]{36}$ ]] || { echo "Invalid game id: $ID" >&2; exit 1; }
+
+if ! curl -s -o /dev/null "$API/listmountzip"; then
+  "$FP_PATH/Server/FlashpointGameServer" -rootPath "$FP_PATH" \
+    -useInfinityServer=false -handleLegacyRequests=true &
+  until curl -s -o /dev/null "$API/listmountzip"; do sleep 0.2; done
+fi
+
+IFS=$'\x1f' read -r app cmd date_added < <(sqlite3 -readonly -separator $'\x1f' "$DB" "
+  select coalesce(nullif(d.applicationPath, ''), g.applicationPath),
+         coalesce(nullif(d.launchCommand, ''), g.launchCommand),
+         coalesce(d.dateAdded, '')
+  from game g left join game_data d on d.id = g.activeDataId
+  where g.id = '$ID'") || true
+[[ -n ${app:-} ]] || { echo "Game not found: $ID" >&2; exit 1; }
+
+if [[ -n $date_added ]]; then
+  zip=$FP_PATH/Data/Games/$ID-$(date -u -d "$date_added" +%s%3N).zip
+  curl -sf -X POST -H 'Content-Type: application/json' \
+    -d "{\"filePath\": \"$zip\"}" "$API/mountzip" >/dev/null ||
+    { echo "Failed to mount $zip" >&2; exit 1; }
+fi
+
+echo "Launching $ID: $app $cmd"
+case ${app,,} in
+  'fpsoftware\startjava.bat' | 'fpsoftware\startjavainbrowser.bat')
+    FP_PATH=$FP_PATH exec "$FP_PATH/FPSoftware/startJava.sh" "$cmd" ;;
+  *)
+    echo "Unsupported application: $app" >&2; exit 1 ;;
+esac