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/core/dal/metrics_repository.py

@@ -0,0 +1,53 @@
+from core.dal.base_repository import BaseRepository
+
+
+class MetricsRepository(BaseRepository):
+
+    def insert(
+        self, server_id: int, cpu_percent: float, ram_mb: float = 0.0, player_count: int = 0
+    ) -> None:
+        self._execute(
+            """
+            INSERT INTO metrics (server_id, cpu_percent, ram_mb, player_count)
+            VALUES (:sid, :cpu, :ram, :pc)
+            """,
+            {"sid": server_id, "cpu": cpu_percent, "ram": ram_mb, "pc": player_count},
+        )
+
+    def query(
+        self,
+        server_id: int,
+        from_ts: str | None = None,
+        to_ts: str | None = None,
+    ) -> list[dict]:
+        conditions = ["server_id = :sid"]
+        params: dict = {"sid": server_id}
+        if from_ts:
+            conditions.append("timestamp >= :from_ts")
+            params["from_ts"] = from_ts
+        if to_ts:
+            conditions.append("timestamp <= :to_ts")
+            params["to_ts"] = to_ts
+        where = " AND ".join(conditions)
+        return self._fetchall(
+            f"SELECT * FROM metrics WHERE {where} ORDER BY timestamp ASC",
+            params,
+        )
+
+    def get_latest(self, server_id: int) -> dict | None:
+        return self._fetchone(
+            "SELECT * FROM metrics WHERE server_id = :sid ORDER BY timestamp DESC LIMIT 1",
+            {"sid": server_id},
+        )
+
+    def cleanup_old(self, retention_days: int = 1, server_id: int | None = None) -> None:
+        if server_id is not None:
+            self._execute(
+                "DELETE FROM metrics WHERE server_id = :sid AND timestamp < datetime('now', :delta)",
+                {"sid": server_id, "delta": f"-{retention_days} days"},
+            )
+        else:
+            self._execute(
+                "DELETE FROM metrics WHERE timestamp < datetime('now', :delta)",
+                {"delta": f"-{retention_days} days"},
+            )