Remove env var overrides, config.yaml is single source of truth

- Stripped _ENV_MAP and _apply_env_overrides from configs/load.py
- Cleaned up unused imports in video_receiver.py
- Restored MediaPipe env suppressors in app/main.py
- Removed .env.example (replaced by config.yaml)

configs/load.py

@@ -1,7 +1,6 @@
 from __future__ import annotations
 
 import dataclasses
-import os
 from pathlib import Path
 from typing import Any
 
@@ -19,24 +18,6 @@ from configs.models import (
 
 _PROJECT_ROOT = Path(__file__).resolve().parent.parent
 
-_ENV_MAP = {
-    "POSEFIT_WS_HOST": ("server", "host"),
-    "POSEFIT_WS_PORT": ("server", "port", int),
-    "POSEFIT_WS_MAX_SIZE": ("server", "max_ws_size", int),
-    "POSEFIT_PROCESS_EVERY_N_FRAMES": ("video", "process_every_n_frames", int),
-    "POSEFIT_MODEL_PATH": ("model", "path"),
-    "POSEFIT_PREFER_GPU": ("model", "prefer_gpu", lambda v: v not in ("0", "false", "False")),
-    "POSEFIT_VISIBILITY_THRESHOLD": ("dead_bug", "visibility_threshold", float),
-    "POSEFIT_EXTENSION_CONFIRM_FRAMES": ("dead_bug", "extension_confirm_frames", int),
-    "POSEFIT_RESET_CONFIRM_FRAMES": ("dead_bug", "reset_confirm_frames", int),
-    "POSEFIT_REP_ANNOUNCER_ENABLED": ("audio", "rep_announcer_enabled", lambda v: v not in ("0", "false", "False")),
-    "POSEFIT_REP_ANNOUNCER_RATE": ("audio", "rep_announcer_rate", int),
-    "POSEFIT_REP_ANNOUNCER_VOLUME": ("audio", "rep_announcer_volume", float),
-    "POSEFIT_LOG_ROTATION": ("logging", "rotation"),
-    "POSEFIT_LOG_RETENTION": ("logging", "retention"),
-    "POSEFIT_LOG_DIR": ("logging", "dir"),
-}
-
 _SECTION_CLASS = {
     "server": ServerConfig,
     "video": VideoConfig,
@@ -61,22 +42,11 @@ def _read_yaml(path: Path) -> dict[str, Any]:
         return yaml.safe_load(f) or {}
 
 
-def _apply_env_overrides(raw: dict[str, Any]) -> None:
-    for env_var, (section, key, *rest) in _ENV_MAP.items():
-        value = os.getenv(env_var)
-        if value is None:
-            continue
-        if rest:
-            value = rest[0](value)
-        raw.setdefault(section, {})[key] = value
-
-
 def load_config(config_path: str | Path | None = None) -> AppConfig:
     if config_path is None:
         config_path = _PROJECT_ROOT / "config.yaml"
 
     raw = _read_yaml(Path(config_path))
-    _apply_env_overrides(raw)
 
     return AppConfig(**{
         section: cls(**_dict_to_dataclass(cls, raw.get(section)))