Fix build errors in ifp_egm.md

- Change equation label from 'eqvfs' to 'eqvfs_egm' to avoid duplicate with ifp_discrete.md
- Add missing closing backticks after solution-end directives

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: jstac

lectures/ifp_egm.md

@@ -175,7 +175,7 @@ Optimality is defined below.
 The **value function** $V \colon \mathsf S \to \mathbb{R}$ is defined by
 
 ```{math}
-:label: eqvfs
+:label: eqvfs_egm
 
 V(a, z) := \max \, \mathbb{E}
 \left\{