feat(postgres): Move to array storage

[devsjc]

Moves the storage format over to arrays. All reads become dual channel because the transition will take some time. After all partitions have been moved over, this dual behaviour can be stopped.

[github-actions]

Benchmark Results

Benchmark results

?   	github.com/openclimatefix/data-platform/cmd	[no test files]
?   	github.com/openclimatefix/data-platform/internal/gen/ocf/dp	[no test files]
?   	github.com/openclimatefix/data-platform/internal/interceptors	[no test files]
PASS
ok  	github.com/openclimatefix/data-platform/internal/server/dummy	0.005s
{"level":"debug","time":"2026-08-11T16:32:57Z","message":"Completed migrations"}
goos: linux
goarch: amd64
pkg: github.com/openclimatefix/data-platform/internal/server/postgres
cpu: AMD EPYC 9V74 80-Core Processor                
BenchmarkPostgresClient/small/GetForecastAsTimeseries-4         	     133	   8828015 ns/op
BenchmarkPostgresClient/small/GetForecastAtTimestamp-4          	     314	   3655141 ns/op
BenchmarkPostgresClient/small/GetObservationsAsTimeseries-4     	     998	   1146792 ns/op
BenchmarkPostgresClient/small/CreateForecast-4                  	     109	  10584163 ns/op
BenchmarkPostgresClient/small/StreamForecastData-4              	      27	  42211895 ns/op
PASS
ok  	github.com/openclimatefix/data-platform/internal/server/postgres	60.757s
?   	github.com/openclimatefix/data-platform/internal/server/postgres/gen	[no test files]