feat: implement full backend + frontend server detail, settings, and create server pages

Backend:
- Complete FastAPI backend with 42+ REST endpoints (auth, servers, config,
  players, bans, missions, mods, games, system)
- Game adapter architecture with Arma 3 as first-class adapter
- WebSocket real-time events for status, metrics, logs, players
- Background thread system (process monitor, metrics, log tail, RCon poller)
- Fernet encryption for sensitive config fields at rest
- JWT auth with admin/viewer roles, bcrypt password hashing
- SQLite with WAL mode, parameterized queries, migration system
- APScheduler cleanup jobs for logs, metrics, events

Frontend:
- Server Detail page with 7 tabs (overview, config, players, bans,
  missions, mods, logs)
- Settings page with password change and admin user management
- Create Server wizard (4-step; known bug: silent validation failure)
- New hooks: useServerDetail, useAuth, useGames
- New components: ServerHeader, ConfigEditor, PlayerTable, BanTable,
  MissionList, ModList, LogViewer, PasswordChange, UserManager
- WebSocket onEvent callback for real-time log accumulation
- 120 unit tests passing (Vitest + React Testing Library)

Docs:
- Added .gitignore, CLAUDE.md, README.md
- Updated FRONTEND.md, ARCHITECTURE.md with current implementation state
- Added .env.example for backend configuration

Known issues:
- Create Server form: "Next" buttons don't validate before advancing,
  causing silent submit failure when fields are invalid
- Config sub-tabs need UX redesign for non-technical users

backend/adapters/arma3/rcon_service.py

@@ -0,0 +1,142 @@
+"""Arma 3 RCon service — remote admin via BattleEye RCon protocol."""
+from __future__ import annotations
+
+import socket
+import logging
+import struct
+from typing import Any
+
+from pydantic import BaseModel
+
+logger = logging.getLogger(__name__)
+
+
+class Arma3PlayerData(BaseModel):
+    """Player data schema for Arma 3."""
+    name: str
+    ping: int = 0
+    guid: str = ""
+
+
+class Arma3RConClient:
+    """BattleEye RCon client for a single connection."""
+
+    def __init__(self, host: str, port: int, password: str):
+        self._host = host
+        self._port = port
+        self._password = password
+        self._sock: socket.socket | None = None
+
+    def _connect(self) -> None:
+        if self._sock is not None:
+            return
+        self._sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        self._sock.settimeout(5.0)
+        self._sock.connect((self._host, self._port))
+        # Login sequence
+        self._login()
+
+    def _login(self) -> None:
+        if self._sock is None:
+            raise ConnectionError("Not connected")
+        # BE RCon login: send password with checksum
+        password_bytes = self._password.encode("utf-8")
+        checksum = self._compute_checksum(password_bytes)
+        packet = b"\xff" + bytes([0, len(password_bytes) & 0xff]) + checksum + password_bytes
+        self._sock.send(packet)
+        response = self._sock.recv(4096)
+        if not response or response[0] != 0xff:
+            raise ConnectionError("RCon login failed")
+
+    @staticmethod
+    def _compute_checksum(data: bytes) -> bytes:
+        """Compute BE RCon checksum (sum of bytes) & 0xFF."""
+        return bytes([sum(data) & 0xFF])
+
+    def send_command(self, command: str, timeout: float = 5.0) -> str | None:
+        try:
+            self._connect()
+            if self._sock is None:
+                return None
+            self._sock.settimeout(timeout)
+            cmd_bytes = command.encode("utf-8")
+            checksum = self._compute_checksum(cmd_bytes)
+            packet = b"\xff\x01" + bytes([len(cmd_bytes) & 0xff]) + checksum + cmd_bytes
+            self._sock.send(packet)
+            response = self._sock.recv(4096)
+            if response and len(response) > 2:
+                return response[2:].decode("utf-8", errors="replace")
+            return None
+        except Exception as e:
+            logger.error("RCon command error: %s", e)
+            return None
+
+    def get_players(self) -> list[dict]:
+        result = self.send_command("players")
+        if result is None:
+            return []
+        # Parse player list from BE RCon response
+        players = []
+        for line in result.split("\n"):
+            line = line.strip()
+            if not line or line.startswith("(") or line.startswith("total"):
+                continue
+            parts = line.split(maxsplit=4)
+            if len(parts) >= 5:
+                players.append({
+                    "slot_id": parts[0],
+                    "name": parts[3] if len(parts) > 3 else "",
+                    "guid": parts[2] if len(parts) > 2 else "",
+                    "ping": int(parts[1]) if parts[1].isdigit() else 0,
+                })
+        return players
+
+    def kick_player(self, identifier: str, reason: str = "") -> bool:
+        cmd = f"kick {identifier}"
+        if reason:
+            cmd += f" {reason}"
+        result = self.send_command(cmd)
+        return result is not None
+
+    def ban_player(self, identifier: str, duration_minutes: int, reason: str) -> bool:
+        cmd = f"ban {identifier} {duration_minutes} {reason}"
+        result = self.send_command(cmd)
+        return result is not None
+
+    def say_all(self, message: str) -> bool:
+        result = self.send_command(f"say {message}")
+        return result is not None
+
+    def shutdown(self) -> bool:
+        result = self.send_command("#shutdown")
+        return result is not None
+
+    def keepalive(self) -> None:
+        try:
+            self.send_command("")
+        except Exception as exc:
+            logger.debug("Arma3RConClient: keepalive failed: %s", exc)
+
+    def disconnect(self) -> None:
+        if self._sock:
+            try:
+                self._sock.close()
+            except Exception as exc:
+                logger.debug("Arma3RConClient: error closing socket: %s", exc)
+            self._sock = None
+
+
+class Arma3RConService:
+    """Factory for Arma 3 RCon clients."""
+
+    def create_client(self, host: str, port: int, password: str) -> Arma3RConClient:
+        return Arma3RConClient(host, port, password)
+
+    def get_startup_delay(self) -> float:
+        return 30.0
+
+    def get_poll_interval(self) -> float:
+        return 10.0
+
+    def get_player_data_schema(self) -> type[BaseModel] | None:
+        return Arma3PlayerData