feat(forecast-timestamp): add init and creation to GetForecastAtTimes…

[peterdudfield]

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?

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Changes in this Pull Request

Add inti and creation time to theGetForecastAtTimestamp route

I ran it locally with the development database. It worked

[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":"2026-03-23T19:11:30Z","message":"Completed migrations"}
goos: linux
goarch: amd64
pkg: github.com/openclimatefix/data-platform/internal/server/postgres
cpu: Intel(R) Xeon(R) Platinum 8370C CPU @ 2.80GHz
BenchmarkPostgresClient/small/GetForecastAsTimeseries-4         	      55	  20878736 ns/op
BenchmarkPostgresClient/small/GetForecastAtTimestamp-4          	      64	  15666410 ns/op
BenchmarkPostgresClient/small/GetObservationsAsTimeseries-4     	    1123	   1061220 ns/op
BenchmarkPostgresClient/small/CreateForecast-4                  	      86	  13758973 ns/op
PASS
ok  	github.com/openclimatefix/data-platform/internal/server/postgres	64.126s
?   	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 │
                                                   │     sec/op     │
PostgresClient/small/GetForecastAsTimeseries-4         18.65m ± ∞ ¹
PostgresClient/small/GetForecastAtTimestamp-4          14.74m ± ∞ ¹
PostgresClient/small/GetObservationsAsTimeseries-4     1.270m ± ∞ ¹
PostgresClient/small/CreateForecast-4                  14.79m ± ∞ ¹
geomean                                                8.476m
¹ need >= 6 samples for confidence interval at level 0.95

cpu: Intel(R) Xeon(R) Platinum 8370C CPU @ 2.80GHz
                                                   │ bench-add-to-forecast-snapshot.txt │
                                                   │               sec/op               │
PostgresClient/small/GetForecastAsTimeseries-4                             20.88m ± ∞ ¹
PostgresClient/small/GetForecastAtTimestamp-4                              15.67m ± ∞ ¹
PostgresClient/small/GetObservationsAsTimeseries-4                         1.061m ± ∞ ¹
PostgresClient/small/CreateForecast-4                                      13.76m ± ∞ ¹
geomean                                                                    8.313m
¹ need >= 6 samples for confidence interval at level 0.95