Add unified API landing page and fix footer layout #4336

Job	Run time
Detect File Changes	9s
Lint Gate	1m 44s
Github (macos, mpi, debug, false)	54m 30s
Github (ubuntu, no-mpi, single, no-debug, false)	28m 57s
Georgia Tech \| Phoenix (cpu)	1h 15m 20s
Github (ubuntu, mpi, no-debug, false)	2h 14m 57s
Georgia Tech \| Phoenix (gpu-omp)	8h 0m 54s
Github (ubuntu, mpi, debug, true)	1h 45m 6s
Oak Ridge \| Frontier (AMD) (gpu-omp)	7h 16m 31s
Oak Ridge \| Frontier (gpu-acc)	8h 0m 16s
Github (ubuntu, mpi, debug, false)	2h 20m 11s
Oak Ridge \| Frontier (cpu)	4h 33m 3s
Georgia Tech \| Phoenix (gpu-acc)	1h 29m 57s
Oak Ridge \| Frontier (AMD) (cpu)	2h 43m 45s
Github (ubuntu, mpi, no-debug, true)	1h 34m 26s
Oak Ridge \| Frontier (gpu-omp)	7h 45m 41s
Github (macos, mpi, no-debug, false)	1h 29m 24s
	2d 3h 54m 51s

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