feat: implement phases 3-5 of Arma 3 UX enhancement plan

Phase 3 - Mod display names + split-pane selector:
- Parse mod.cpp/meta.cpp for display_name and workshop_id
- Rewrite ModList as two-pane available/selected interface

Phase 4 - Player kick/ban from Players tab:
- Add get_by_slot() to PlayerRepository
- Add get_rcon_client() class method to ThreadRegistry
- Add /players/{slot_id}/kick and /ban endpoints
- Rewrite PlayerTable with kick/ban modals and ban presets

Phase 5 - Historical log file browser:
- Add list_log_files() and get_log_file_path() to RPTParser
- Add logfiles_router with GET/download/DELETE endpoints
- Update LogViewer with collapsible log files section (download + delete)

backend/core/servers/logfiles_router.py

@@ -0,0 +1,80 @@
+"""Log file endpoints — list, download, and delete historical RPT log files."""
+from __future__ import annotations
+
+import logging
+from typing import Annotated
+
+from fastapi import APIRouter, Depends, HTTPException
+from fastapi.responses import FileResponse
+from sqlalchemy.engine import Connection
+
+from adapters.registry import GameAdapterRegistry
+from core.dal.server_repository import ServerRepository
+from core.utils.file_utils import get_server_dir
+from database import get_db
+from dependencies import get_current_user, require_admin
+
+logger = logging.getLogger(__name__)
+
+router = APIRouter(prefix="/servers/{server_id}/logfiles", tags=["logfiles"])
+
+
+def _ok(data):
+    return {"success": True, "data": data, "error": None}
+
+
+def _get_rpt_parser(server_id: int, db: Connection):
+    server = ServerRepository(db).get_by_id(server_id)
+    if server is None:
+        raise HTTPException(status_code=404, detail="Server not found")
+    adapter = GameAdapterRegistry.get(server["game_type"])
+    if not adapter.has_capability("log_parser"):
+        raise HTTPException(status_code=404, detail="Server does not support log files")
+    return adapter.get_log_parser(), get_server_dir(server_id)
+
+
+@router.get("")
+def list_log_files(
+    server_id: int,
+    db: Annotated[Connection, Depends(get_db)],
+    _user: Annotated[dict, Depends(get_current_user)],
+) -> dict:
+    parser, server_dir = _get_rpt_parser(server_id, db)
+    files = parser.list_log_files(server_dir)
+    return _ok(files)
+
+
+@router.get("/{filename}/download")
+def download_log_file(
+    server_id: int,
+    filename: str,
+    db: Annotated[Connection, Depends(get_db)],
+    _user: Annotated[dict, Depends(get_current_user)],
+):
+    parser, server_dir = _get_rpt_parser(server_id, db)
+    path = parser.get_log_file_path(server_dir, filename)
+    if path is None:
+        raise HTTPException(status_code=404, detail="Log file not found")
+    return FileResponse(
+        path=str(path),
+        filename=filename,
+        media_type="text/plain",
+    )
+
+
+@router.delete("/{filename}")
+def delete_log_file(
+    server_id: int,
+    filename: str,
+    db: Annotated[Connection, Depends(get_db)],
+    _admin: Annotated[dict, Depends(require_admin)],
+) -> dict:
+    parser, server_dir = _get_rpt_parser(server_id, db)
+    path = parser.get_log_file_path(server_dir, filename)
+    if path is None:
+        raise HTTPException(status_code=404, detail="Log file not found")
+    try:
+        path.unlink()
+    except OSError as exc:
+        raise HTTPException(status_code=500, detail=f"Could not delete file: {exc}") from exc
+    return _ok({"message": f"{filename} deleted"})