Refactor dotenv loading to use explicit paths in CLI and API modules

[dphuang2]

• improving environment variable management and preventing conflicts with other .env files.

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Note

Standardizes environment loading to avoid accidental parent .env usage.

• CLI: In eval_protocol/cli.py, replace implicit load_dotenv() with explicit paths to .env.dev and .env using dotenv_path, preserving override=True.
• Vercel API: In quickstart/svg_agent/vercel_svg_server/api/init.py, switch to load_dotenv(dotenv_path=Path('.') / '.env').
• MCP client: Remove .env auto-loading from eval_protocol/mcp/mcp_multi_client.py.
• Tests: Add tests/test_no_implicit_dotenv.py to AST-scan repo code and fail CI if any load_dotenv() call lacks an explicit dotenv_path.

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[cursor]

Environment loading removed instead of using explicit path

Medium Severity

The load_dotenv() call was removed entirely from mcp_multi_client.py instead of being replaced with an explicit path like in other files (cli.py, init.py). When MCPMultiClient is used directly (not through the CLI), environment variables from .env files will no longer be loaded. The class still validates that required environment variables exist in _validate_environment_variables(), so this change breaks standalone usage of the module and is inconsistent with the pattern used in other files in this PR.