fix(sql): Correct GetLatestForcast logic

[devsjc]

Contribution Checklist

• Have you followed the Open Climate Fix Contribution Guidelines?
• Have you referenced the Issue this PR addresses, where applicable?
• Have you checked to ensure there aren't other open Pull Requests for the same change?
• Have you added a summary of the changes?
• Have you written new tests for your changes, where applicable?
• Have you successfully run make lint with your changes locally?
• Have you successfully run make test with your changes locally?

Warning

PRs may be closed if all the above boxes are not checked.

Changes in this Pull Request

Fixes a bug in the LatestForecast SQL logic that was incorectly ordering the returned forecasts.

[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":"2026-01-20T16:50:02Z","message":"Completed migrations"}
goos: linux
goarch: amd64
pkg: github.com/openclimatefix/data-platform/internal/server/postgres
cpu: AMD EPYC 7763 64-Core Processor                
BenchmarkPostgresClient/2400000/GetForecastAsTimeseries-4         	       2	 838788893 ns/op
BenchmarkPostgresClient/2400000/GetForecastAtTimestamp-4          	      72	  16289037 ns/op
BenchmarkPostgresClient/2400000/GetObservationsAsTimeseries-4     	     944	   1168317 ns/op
BenchmarkPostgresClient/2400000/CreateForecast-4                  	      55	  20708026 ns/op
PASS
ok  	github.com/openclimatefix/data-platform/internal/server/postgres	316.552s
?   	github.com/openclimatefix/data-platform/internal/server/postgres/gen	[no test files]

Benchmark vs base branch

goos: linux
goarch: amd64
pkg: github.com/openclimatefix/data-platform/internal/server/postgres
cpu: AMD EPYC 7763 64-Core Processor                
                                                     │ bench-main.txt │ bench-devsjc-latest-fix.txt │
                                                     │     sec/op     │        sec/op         vs base   │
PostgresClient/6144000/GetForecastAsTimeseries-4         4.826m ± ∞ ¹
PostgresClient/6144000/GetForecastAtTimestamp-4          105.0m ± ∞ ¹
PostgresClient/6144000/GetObservationsAsTimeseries-4     1.307m ± ∞ ¹
PostgresClient/6144000/CreateForecast-4                  2.612m ± ∞ ¹
PostgresClient/2400000/GetForecastAsTimeseries-4                                838.8m ± ∞ ¹
PostgresClient/2400000/GetForecastAtTimestamp-4                                 16.29m ± ∞ ¹
PostgresClient/2400000/GetObservationsAsTimeseries-4                            1.168m ± ∞ ¹
PostgresClient/2400000/CreateForecast-4                                         20.71m ± ∞ ¹
geomean                                                  6.449m                 23.98m        ? ² ³
¹ need >= 6 samples for confidence interval at level 0.95
² benchmark set differs from baseline; geomeans may not be comparable
³ ratios must be >0 to compute geomean