refactor(app): nest slice components under Nuxt folders (CLEAN-45)

[maksymhryzodub-prog]

Summary

• Nest camelCase app slice component folders under Nuxt entity/feature/Role paths so auto-import names stay the same (AgentListProvider, BridleChat*, LandingHero*, TemplateListProvider, …).
• Move templates.vue to templates/index.vue so it matches agents/ and chats/; route remains /templates.

Jira: CLEAN-45

Test plan

• Auto-import tags still resolve (AgentListProvider, AgentListCard, AgentChatProvider, BridleChatProvider/Input/Empty/Message, TemplateListProvider, LandingHeroProvider, LandingHeroAgentCard)
• /templates still routes
• No leftover components/agentList, agentChat, bridleChat, templateList, or landingHero paths under app/