feat(auth): implement authentication endpoints and JWT handling

app/models/auth.py

@@ -0,0 +1,43 @@
+from datetime import datetime
+
+from pydantic import BaseModel, ConfigDict, Field
+
+
+class AuthUserDocument(BaseModel):
+    model_config = ConfigDict(extra="forbid")
+
+    username: str = Field(
+        ...,
+        description="Unique username for the single account",
+    )
+    password_hash: str = Field(..., description="Hashed password")
+    created_at: datetime | None = Field(
+        default=None,
+        description="Creation timestamp in UTC",
+    )
+    updated_at: datetime | None = Field(
+        default=None,
+        description="Last update timestamp in UTC",
+    )
+
+
+class LoginInput(BaseModel):
+    model_config = ConfigDict(extra="forbid")
+
+    username: str = Field(..., description="Username")
+    password: str = Field(..., description="Plain text password")
+
+
+class TokenResponse(BaseModel):
+    model_config = ConfigDict(extra="forbid")
+
+    access_token: str = Field(..., description="JWT access token")
+    token_type: str = Field(default="bearer", description="Token type")
+
+
+class AccessTokenPayload(BaseModel):
+    model_config = ConfigDict(extra="forbid")
+
+    sub: str = Field(..., description="Subject username")
+    jti: str = Field(..., description="Unique token identifier")
+    exp: int = Field(..., description="Token expiration as unix timestamp")