feat: scaffold FastAPI app, config, and SQLite models

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/app/config.py

@@ -0,0 +1,33 @@
+from pathlib import Path
+
+from pydantic import Field
+from pydantic_settings import BaseSettings, SettingsConfigDict
+
+
+class Settings(BaseSettings):
+    model_config = SettingsConfigDict(
+        env_file=".env",
+        env_file_encoding="utf-8",
+        populate_by_name=True,
+        extra="ignore",
+    )
+
+    data_dir: Path = Field(default=Path("/data"), alias="DATA_DIR")
+    admin_password: str = Field(default="changeme", alias="ADMIN_PASSWORD")
+    secret_key: str = Field(default="dev-secret-change-me", alias="SECRET_KEY")
+    max_upload_mb: int = Field(default=200, alias="MAX_UPLOAD_MB")
+    rate_limit_per_second: int = Field(default=2, alias="RATE_LIMIT_PER_SECOND")
+    jwt_expire_hours: int = Field(default=12, alias="JWT_EXPIRE_HOURS")
+    host: str = Field(default="0.0.0.0", alias="HOST")
+    port: int = Field(default=8080, alias="PORT")
+
+    @property
+    def db_url(self) -> str:
+        return f"sqlite:///{self.data_dir / 'mincedpad.db'}"
+
+    @property
+    def uploads_dir(self) -> Path:
+        return self.data_dir / "uploads"
+
+
+settings = Settings()