Memory scopes, part 2: folder notes, a /scope command in chat apps, and clearer badges #392

Follow-up to #155 / #381 (memory scopes).

1. Folder notes (feat: search local folders and Obsidian vaults as your notes #349): an added folder or vault can be marked Personal, Work, a project or Always, and its notes are recalled only in matching chats. Today folder notes reach every scope.
2. Chat apps: a /scope command (/scope work, /scope personal, /scope <project>) in Telegram, Discord and WhatsApp, with a plain reply saying what changed. Today a chat app's scope can only be set in Settings.
3. Badges: on the Memory screen the scope badge ("Work") and the topic badge ("Work & Learning") look alike. Give the scope badge its own style, or put it under a "Used in" label, so they aren't confused.

Real test: a work folder note that doesn't come up in a personal chat, and /scope work from the fake Telegram API changing what that chat recalls.