Add config file autodiscovery

[mintyPT]

Problem

Config commands require users to pass the config path every time, even when working inside a project with a conventional clickclick.config.json. This adds friction to common workflows.

Proposal

Allow config commands to discover clickclick.config.json from the current directory upward:

clickclick config templates
clickclick config recipe release
clickclick config set social

Explicit config paths should continue to work.

Acceptance criteria

• Config commands work without <config-file> when a config file is found in cwd or a parent directory.
• Explicit config paths preserve current behavior.
• Missing config files produce a clear INVALID_INPUT error with the searched filename.
• Help text documents both modes.
• Tests cover cwd config, parent-directory config, explicit path, and missing config.