Add multi-token authentication with client labels

- Replace single api_token with api_tokens dict (label: token pairs)
- Add context-aware logging to track which client made each request
- Implement token label lookup with secure comparison
- Add logging middleware to inject token labels into request context
- Update logging format to display [label] in all log messages
- Fix WebSocket authentication to use new multi-token system
- Update CLI --show-token to display all tokens with labels
- Update config generation to use api_tokens format
- Update README with multi-token documentation
- Update config.example.yaml with multiple token examples

Benefits:
- Easy identification of clients in logs (Home Assistant, mobile, web UI, etc.)
- Per-client token management and revocation
- Better security and auditability

Example log output:
2026-02-06 03:36:20,806 - [home_assistant] - WebSocket client connected

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

media_server/config.py

@@ -46,9 +46,9 @@ class Settings(BaseSettings):
     port: int = Field(default=8765, description="Server port")
 
     # Authentication
-    api_token: str = Field(
-        default_factory=lambda: secrets.token_urlsafe(32),
-        description="API authentication token",
+    api_tokens: dict[str, str] = Field(
+        default_factory=lambda: {"default": secrets.token_urlsafe(32)},
+        description="Named API tokens for access control (label: token pairs)",
     )
 
     # Media controller settings
@@ -128,7 +128,9 @@ def generate_default_config(path: Optional[Path] = None) -> Path:
     config = {
         "host": "0.0.0.0",
         "port": 8765,
-        "api_token": secrets.token_urlsafe(32),
+        "api_tokens": {
+            "default": secrets.token_urlsafe(32),
+        },
         "poll_interval": 1.0,
         "log_level": "INFO",
         # Audio device to control (use GET /api/audio/devices to list available devices)