feat: improve audio streaming UI and configuration (#11)

- Renamed "AES67" mode to "Network" for clearer user understanding
- Added structured stream controls with consistent start/stop buttons and status display
- Changed presentation delay input from microseconds to milliseconds for better usability
- Restricted retransmission (RTN) options to valid range of 1-4
- Added help tooltips for assisted listening and immediate rendering options
- Fixed portaudio configuration to enable ALSA support and remove

Co-authored-by: pstruebi <struebin.patrick.com>
Reviewed-on: https://gitea.pstruebi.xyz/auracaster/bumble-auracast/pulls/11

src/auracast/utils/frontend_auth.py

@@ -25,17 +25,15 @@ def is_pw_disabled() -> bool:
     return str(val).strip().lower() in ("1", "true", "yes", "on")
 
 
-# Storage paths and permissions
+# Storage paths and permissions (store next to multicast_frontend.py)
 
 def state_dir() -> Path:
-    custom = os.getenv("AURACAST_STATE_DIR")
-    if custom:
-        return Path(custom).expanduser()
-    return Path.home() / ".config" / "auracast"
+    # utils/ -> auracast/ -> server/
+    return Path(__file__).resolve().parents[1] / "server"
 
 
 def pw_file_path() -> Path:
-    return state_dir() / "frontend_pw.json"
+    return state_dir() / "credentials.json"
 
 
 def ensure_state_dir() -> None: