Add real-time system stats (CPU/RAM/GPU/VRAM) and fix favicon

Favicon now matches the LokiMark topbar icon instead of an unrelated
arrow glyph. New /api/system/stats endpoint (psutil + nvidia-smi)
polled every 2s and shown in the topbar next to the Ollama status.

backend/app/main.py

@@ -14,7 +14,7 @@ from fastapi.staticfiles import StaticFiles
 
 from . import db
 from .config import settings
-from .routes import chat, config, files, models, sessions, shell
+from .routes import chat, config, files, models, sessions, shell, system
 
 
 @asynccontextmanager
@@ -42,6 +42,7 @@ app.include_router(chat.router)
 app.include_router(files.router)
 app.include_router(config.router)
 app.include_router(shell.router)
+app.include_router(system.router)
 
 
 @app.get("/api/health")