flake.lock: Update

Flake lock file updates:

• Updated input 'haskell-nix':
    'github:input-output-hk/haskell.nix/cad2645' (2026-01-03)
  → 'github:input-output-hk/haskell.nix/131f8cc' (2026-05-16)
• Removed input 'haskell-nix/cabal-32'
• Updated input 'haskell-nix/hackage':
    'github:input-output-hk/hackage.nix/05797dd' (2026-01-03)
  → 'github:input-output-hk/hackage.nix/a482aef' (2026-05-16)
• Updated input 'haskell-nix/hackage-for-stackage':
    'github:input-output-hk/hackage.nix/fba3874' (2026-01-03)
  → 'github:input-output-hk/hackage.nix/ab71329' (2026-05-16)
• Added input 'haskell-nix/hls-2.12':
    'github:haskell/haskell-language-server/7d983de' (2025-09-24)
• Updated input 'haskell-nix/iserv-proxy':
    'github:stable-haskell/iserv-proxy/1506051' (2025-08-15)
  → 'github:stable-haskell/iserv-proxy/3f7b281' (2026-04-08)
• Updated input 'haskell-nix/nixpkgs-2511':
    'github:NixOS/nixpkgs/b0924ea' (2025-12-01)
  → 'github:NixOS/nixpkgs/74b8795' (2026-04-09)
• Updated input 'haskell-nix/nixpkgs-unstable':
    'github:NixOS/nixpkgs/c1cb7d0' (2025-12-01)
  → 'github:NixOS/nixpkgs/1304392' (2026-04-11)
• Updated input 'haskell-nix/stackage':
    'github:input-output-hk/stackage.nix/8a7333a' (2026-01-03)
  → 'github:input-output-hk/stackage.nix/c1f217f' (2026-05-16)

Author: github-actions[bot]