feat: make authentication optional — no tokens = no auth

When no api_tokens are configured (the new default), all endpoints
are accessible without authentication. The frontend detects this
via /api/health's auth_required field and skips the login form.

- Backend: auth.py skips verification when api_tokens is empty
- Frontend: shared getAuthHeaders()/hasCredentials() helpers replace
  scattered token logic across all JS modules
- Health endpoint exposes auth_required for frontend discovery
- config.example.yaml ships with tokens commented out
- CLI --show-token and startup log reflect disabled state

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

media_server/main.py

@@ -59,9 +59,12 @@ async def lifespan(app: FastAPI):
     logger = logging.getLogger(__name__)
     logger.info(f"Media Server starting on {settings.host}:{settings.port}")
 
-    # Log all configured tokens
-    for label, token in settings.api_tokens.items():
-        logger.info(f"API Token [{label}]: {token[:8]}...")
+    # Log authentication status
+    if settings.api_tokens:
+        for label, token in settings.api_tokens.items():
+            logger.info(f"API Token [{label}]: {token[:8]}...")
+    else:
+        logger.warning("No API tokens configured — authentication is DISABLED")
 
     # Start WebSocket status monitor
     controller = get_media_controller()
@@ -129,24 +132,28 @@ def create_app() -> FastAPI:
     @app.middleware("http")
     async def token_logging_middleware(request: Request, call_next):
         """Extract token label and set in context for logging."""
-        token_label = "unknown"
+        if not settings.api_tokens:
+            token_label_var.set("anonymous")
+        else:
+            token_label = "unknown"
 
-        # Try Authorization header
-        auth_header = request.headers.get("authorization", "")
-        if auth_header.startswith("Bearer "):
-            token = auth_header[7:]
-            label = get_token_label(token)
-            if label:
-                token_label = label
+            # Try Authorization header
+            auth_header = request.headers.get("authorization", "")
+            if auth_header.startswith("Bearer "):
+                token = auth_header[7:]
+                label = get_token_label(token)
+                if label:
+                    token_label = label
 
-        # Try query parameter (for artwork endpoint)
-        elif "token" in request.query_params:
-            token = request.query_params["token"]
-            label = get_token_label(token)
-            if label:
-                token_label = label
+            # Try query parameter (for artwork endpoint)
+            elif "token" in request.query_params:
+                token = request.query_params["token"]
+                label = get_token_label(token)
+                if label:
+                    token_label = label
+
+            token_label_var.set(token_label)
 
-        token_label_var.set(token_label)
         response = await call_next(request)
         return response
 
@@ -215,14 +222,17 @@ def main():
     if args.generate_config:
         config_path = generate_default_config()
         print(f"Configuration file generated at: {config_path}")
-        print("API Token has been saved to the config file.")
+        print("Authentication is disabled by default. Add api_tokens to enable it.")
         return
 
     if args.show_token:
         print(f"Config directory: {get_config_dir()}")
-        print("\nAPI Tokens:")
-        for label, token in settings.api_tokens.items():
-            print(f"  {label:20} {token}")
+        if settings.api_tokens:
+            print("\nAPI Tokens:")
+            for label, token in settings.api_tokens.items():
+                print(f"  {label:20} {token}")
+        else:
+            print("\nAuthentication is DISABLED (no tokens configured)")
         return
 
     uvicorn.run(