Implement configuration loader module

This commit implements a robust configuration loader using Pydantic Settings that handles:

Features:
- Environment variable loading with .env file support
- Type validation and field constraints
- Gitea configuration (URL, token, owner, repo)
- HTTP server configuration (host, port)
- Optional HTTP authentication token
- Optional tool filtering (enabled/disabled tool lists)

Implementation:
- GiteaSettings class with Pydantic validation
- URL validation ensuring http:// or https:// prefix
- Helper properties for parsing comma-separated tool lists
- get_gitea_mcp_env() method to pass config to wrapped MCP server
- load_settings() factory function with optional env_file path

Documentation:
- .env.example template with all configuration options
- Comprehensive docstrings and type hints

This module unblocks both the tool filtering (#12) and HTTP authentication middleware (#13) implementations.

Closes #11

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.env.example

@@ -0,0 +1,16 @@
+# Gitea Configuration
+GITEA_URL=https://gitea.example.com
+GITEA_TOKEN=your_gitea_api_token_here
+GITEA_OWNER=your_username_or_org
+GITEA_REPO=your_repo_name
+
+# HTTP Server Configuration
+HTTP_HOST=127.0.0.1
+HTTP_PORT=8000
+
+# Authentication Configuration (Optional)
+# AUTH_TOKEN=your_bearer_token_here
+
+# Tool Filtering Configuration (Optional)
+# ENABLED_TOOLS=list_issues,create_issue,update_issue
+# DISABLED_TOOLS=delete_issue,close_milestone

src/gitea_http_wrapper/config/__init__.py

@@ -1,3 +1,5 @@
 """Configuration loader module."""
 
-__all__ = []
+from .settings import GiteaSettings, load_settings
+
+__all__ = ["GiteaSettings", "load_settings"]

src/gitea_http_wrapper/config/settings.py

@@ -0,0 +1,113 @@
+"""Configuration settings for Gitea HTTP MCP wrapper."""
+
+from pathlib import Path
+from typing import Optional
+
+from pydantic import Field, field_validator
+from pydantic_settings import BaseSettings, SettingsConfigDict
+
+
+class GiteaSettings(BaseSettings):
+    """Configuration settings loaded from environment or .env file."""
+
+    model_config = SettingsConfigDict(
+        env_file=".env",
+        env_file_encoding="utf-8",
+        case_sensitive=False,
+        extra="ignore",
+    )
+
+    # Gitea Configuration
+    gitea_url: str = Field(
+        ...,
+        description="Gitea instance URL (e.g., https://git.example.com)",
+    )
+    gitea_token: str = Field(
+        ...,
+        description="Gitea API token for authentication",
+    )
+    gitea_owner: str = Field(
+        ...,
+        description="Default repository owner/organization",
+    )
+    gitea_repo: str = Field(
+        ...,
+        description="Default repository name",
+    )
+
+    # HTTP Server Configuration
+    http_host: str = Field(
+        default="127.0.0.1",
+        description="HTTP server bind address",
+    )
+    http_port: int = Field(
+        default=8000,
+        ge=1,
+        le=65535,
+        description="HTTP server port",
+    )
+
+    # Authentication Configuration
+    auth_token: Optional[str] = Field(
+        default=None,
+        description="Bearer token for HTTP authentication (optional)",
+    )
+
+    # Tool Filtering Configuration
+    enabled_tools: Optional[str] = Field(
+        default=None,
+        description="Comma-separated list of enabled tools (optional, enables all if not set)",
+    )
+    disabled_tools: Optional[str] = Field(
+        default=None,
+        description="Comma-separated list of disabled tools (optional)",
+    )
+
+    @field_validator("gitea_url")
+    @classmethod
+    def validate_gitea_url(cls, v: str) -> str:
+        """Ensure Gitea URL is properly formatted."""
+        if not v.startswith(("http://", "https://")):
+            raise ValueError("gitea_url must start with http:// or https://")
+        return v.rstrip("/")
+
+    @property
+    def enabled_tools_list(self) -> Optional[list[str]]:
+        """Parse enabled_tools into a list."""
+        if not self.enabled_tools:
+            return None
+        return [tool.strip() for tool in self.enabled_tools.split(",") if tool.strip()]
+
+    @property
+    def disabled_tools_list(self) -> Optional[list[str]]:
+        """Parse disabled_tools into a list."""
+        if not self.disabled_tools:
+            return None
+        return [tool.strip() for tool in self.disabled_tools.split(",") if tool.strip()]
+
+    def get_gitea_mcp_env(self) -> dict[str, str]:
+        """Get environment variables for the wrapped Gitea MCP server."""
+        return {
+            "GITEA_BASE_URL": self.gitea_url,
+            "GITEA_API_TOKEN": self.gitea_token,
+            "GITEA_DEFAULT_OWNER": self.gitea_owner,
+            "GITEA_DEFAULT_REPO": self.gitea_repo,
+        }
+
+
+def load_settings(env_file: Optional[Path] = None) -> GiteaSettings:
+    """
+    Load settings from environment or .env file.
+
+    Args:
+        env_file: Optional path to .env file. If not provided, searches for .env in current directory.
+
+    Returns:
+        GiteaSettings instance with loaded configuration.
+
+    Raises:
+        ValidationError: If required settings are missing or invalid.
+    """
+    if env_file:
+        return GiteaSettings(_env_file=env_file)
+    return GiteaSettings()