Add favorites to bookmark frequently used meme templates

I use the same 5-6 meme templates all the time but have to search for them every time.

**Current problem:**
- Always scrolling to find my favorite templates
- No way to bookmark templates I use often
- Waste time searching for same memes repeatedly

**Requested feature:**
- Heart button on each template
- Favorites section to see bookmarked templates
- Quick access to most-used memes

Would make the whole experience much faster for regular users like me.

No files, tests, or entry points are named. Start by locating the template listing and its rendering components, then determine how template selections are stored and where a favorites section could fit. Done means users can mark templates, revisit them in a favorites view, and access them without searching.

Written by the indexing model from the issue text.