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/mod_manager.py

@@ -0,0 +1,165 @@
+"""Arma 3 mod manager — handles mod folder conventions, CLI args, and enable/disable."""
+from __future__ import annotations
+
+import logging
+import re
+from pathlib import Path
+
+from pydantic import BaseModel
+
+from adapters.exceptions import AdapterError
+from core.utils.file_utils import get_server_dir
+
+logger = logging.getLogger(__name__)
+
+_MOD_DIR_PATTERN = re.compile(r"^@.+", re.IGNORECASE)
+
+
+class Arma3ModData(BaseModel):
+    """Mod data schema for Arma 3."""
+    workshop_id: str = ""
+    is_server_mod: bool = False
+
+
+class Arma3ModManager:
+
+    def __init__(self, server_id: int | None = None) -> None:
+        self._server_id = server_id
+
+    def _server_dir(self) -> Path:
+        return get_server_dir(self._server_id)
+
+    # ── File / DB operations ──
+
+    def list_available_mods(self) -> list[dict]:
+        """
+        Scan the server directory for mod folders (directories starting with '@').
+
+        Returns list of dicts:
+            name: str        — directory name (e.g. "@CBA_A3")
+            path: str        — absolute directory path
+            size_bytes: int  — total directory size (approximate, non-recursive)
+        """
+        server_dir = self._server_dir()
+        if not server_dir.exists():
+            return []
+
+        mods = []
+        try:
+            for entry in server_dir.iterdir():
+                if entry.is_dir() and _MOD_DIR_PATTERN.match(entry.name):
+                    try:
+                        size = sum(
+                            f.stat().st_size
+                            for f in entry.iterdir()
+                            if f.is_file()
+                        )
+                    except OSError:
+                        size = 0
+                    mods.append({
+                        "name": entry.name,
+                        "path": str(entry.resolve()),
+                        "size_bytes": size,
+                    })
+        except OSError as exc:
+            raise AdapterError(f"Cannot scan mod directory: {exc}") from exc
+
+        mods.sort(key=lambda m: m["name"].lower())
+        return mods
+
+    def get_enabled_mods(self, config_repo) -> list[str]:
+        """
+        Get the list of enabled mod names from the database config.
+
+        Args:
+            config_repo: ConfigRepository instance.
+
+        Returns list of mod directory names (e.g. ["@CBA_A3", "@ace"]).
+        """
+        mods_section = config_repo.get_section(self._server_id, "mods")
+        if mods_section is None:
+            return []
+        enabled = mods_section.get("enabled_mods", [])
+        if isinstance(enabled, str):
+            enabled = [m.strip() for m in enabled.split(",") if m.strip()]
+        return enabled
+
+    def set_enabled_mods(self, mod_names: list[str], config_repo) -> None:
+        """
+        Update the enabled mods list in the database config.
+
+        Args:
+            mod_names: List of mod directory names to enable.
+            config_repo: ConfigRepository instance.
+
+        Raises AdapterError if any mod name doesn't exist on disk.
+        """
+        available = {m["name"] for m in self.list_available_mods()}
+        for name in mod_names:
+            if not _MOD_DIR_PATTERN.match(name):
+                raise AdapterError(f"Invalid mod name '{name}': must start with '@'")
+            if name not in available:
+                raise AdapterError(
+                    f"Mod '{name}' not found in server directory. "
+                    f"Available: {sorted(available)}"
+                )
+
+        mods_section = config_repo.get_section(self._server_id, "mods") or {}
+        current_version = mods_section.get("config_version", 0)
+        config_repo.upsert_section(
+            server_id=self._server_id,
+            section="mods",
+            data={"enabled_mods": mod_names},
+            expected_version=current_version,
+        )
+        logger.info(
+            "Updated enabled mods for server %d: %s",
+            self._server_id, mod_names,
+        )
+
+    # ── CLI argument building ──
+
+    def get_mod_folder_pattern(self) -> str:
+        """Arma 3 mods use @ prefix for local, or numeric workshop IDs."""
+        return "@*"
+
+    def build_mod_args(self, server_mods: list[dict]) -> list[str]:
+        """
+        Build Arma 3 mod CLI arguments.
+        Returns -mod and -serverMod argument lists.
+        """
+        client_mods = []
+        server_only_mods = []
+
+        for mod in server_mods:
+            path = mod.get("folder_path", "")
+            game_data = mod.get("game_data", {})
+            if isinstance(game_data, str):
+                import json
+                try:
+                    game_data = json.loads(game_data)
+                except (json.JSONDecodeError, TypeError):
+                    game_data = {}
+
+            is_server = game_data.get("is_server_mod", False) if isinstance(game_data, dict) else False
+
+            if is_server:
+                server_only_mods.append(path)
+            else:
+                client_mods.append(path)
+
+        args = []
+        if client_mods:
+            args.append('-mod="' + ";".join(client_mods) + '"')
+        if server_only_mods:
+            args.append('-serverMod="' + ";".join(server_only_mods) + '"')
+        return args
+
+    def validate_mod_folder(self, path: Path) -> bool:
+        """Validate that a path looks like a valid Arma 3 mod folder."""
+        if not path.exists() or not path.is_dir():
+            return False
+        return (path / "addons").exists() or (path / "$PREFIX$").exists()
+
+    def get_mod_data_schema(self) -> type[BaseModel] | None:
+        return Arma3ModData