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/config.py

@@ -0,0 +1,35 @@
+"""Load and validate all environment variables at startup."""
+from __future__ import annotations
+
+from pydantic_settings import BaseSettings, SettingsConfigDict
+
+
+class Settings(BaseSettings):
+    model_config = SettingsConfigDict(
+        env_prefix="LANGUARD_",
+        env_file=".env",
+        env_file_encoding="utf-8",
+        case_sensitive=False,
+        # Enable JSON parsing for complex types (list[str]) from env vars
+        json_parse_ints=False,
+    )
+
+    secret_key: str
+    encryption_key: str          # Fernet base64 key
+    db_path: str = "./languard.db"
+    servers_dir: str = "./servers"
+    host: str = "0.0.0.0"
+    port: int = 8000
+    cors_origins: list[str] = ["http://localhost:5173"]
+    log_retention_days: int = 7
+    metrics_retention_days: int = 30
+    player_history_retention_days: int = 90
+    jwt_expire_hours: int = 24
+    login_rate_limit: str = "5/minute"
+    log_level: str = "INFO"
+
+    # Game-specific defaults (used by adapters, not core)
+    arma3_default_exe: str = "C:/Arma3Server/arma3server_x64.exe"
+
+
+settings = Settings()