feat: add git-consistent memory gateway architecture

gateway/app/config.py

@@ -0,0 +1,41 @@
+from __future__ import annotations
+
+from functools import lru_cache
+from pathlib import Path
+
+from pydantic import Field, model_validator
+from pydantic_settings import BaseSettings, SettingsConfigDict
+
+
+class Settings(BaseSettings):
+    model_config = SettingsConfigDict(env_file=".env", env_file_encoding="utf-8", extra="ignore")
+
+    app_name: str = "memory-gateway"
+    app_env: str = "dev"
+    default_branch: str = "main"
+
+    git_remote_url: str = Field(default="", description="Upstream git remote URL or local path")
+    git_mirror_path: Path = Path("/data/git-mirror/repo.git")
+    workspaces_root: Path = Path("/data/workspaces")
+    workspace_state_dir: Path | None = None
+
+    qmd_binary: str = "qmd"
+    qmd_timeout_seconds: int = 300
+    qmd_top_k: int = 5
+    qmd_index_prefix: str = "ws"
+    qmd_update_on_latest_query: bool = True
+    qmd_embed_on_change: bool = True
+
+    xdg_cache_home: Path = Path("/var/lib/qmd/cache")
+    xdg_config_home: Path = Path("/var/lib/qmd/config")
+
+    @model_validator(mode="after")
+    def _normalize_paths(self) -> "Settings":
+        if self.workspace_state_dir is None:
+            self.workspace_state_dir = self.workspaces_root / ".gateway-state"
+        return self
+
+
+@lru_cache(maxsize=1)
+def get_settings() -> Settings:
+    return Settings()