feat(sql): Modify partition scheme for pgvs

[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?

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Changes in this Pull Request

Aligns partitioning in the forecasts and predeicted_generation_values tables for speedier querying.

[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":"2026-03-24T11:16:47Z","message":"Completed migrations"}
goos: linux
goarch: amd64
pkg: github.com/openclimatefix/data-platform/internal/server/postgres
cpu: AMD EPYC 7763 64-Core Processor                
BenchmarkPostgresClient/small/GetForecastAsTimeseries-4         	      66	  17288058 ns/op
BenchmarkPostgresClient/small/GetForecastAtTimestamp-4          	      79	  15007431 ns/op
BenchmarkPostgresClient/small/GetObservationsAsTimeseries-4     	     894	   1269202 ns/op
BenchmarkPostgresClient/small/CreateForecast-4                  	      88	  13041524 ns/op
PASS
ok  	github.com/openclimatefix/data-platform/internal/server/postgres	72.293s
?   	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-pgv-partition-by-forecast-uuid.txt │
                                                   │     sec/op     │         sec/op           vs base                │
PostgresClient/small/GetForecastAsTimeseries-4         21.08m ± ∞ ¹              17.29m ± ∞ ¹       ~ (p=1.000 n=1) ²
PostgresClient/small/GetForecastAtTimestamp-4          14.82m ± ∞ ¹              15.01m ± ∞ ¹       ~ (p=1.000 n=1) ²
PostgresClient/small/GetObservationsAsTimeseries-4     1.207m ± ∞ ¹              1.269m ± ∞ ¹       ~ (p=1.000 n=1) ²
PostgresClient/small/CreateForecast-4                  14.63m ± ∞ ¹              13.04m ± ∞ ¹       ~ (p=1.000 n=1) ²
geomean                                                8.620m                    8.095m        -6.08%
¹ need >= 6 samples for confidence interval at level 0.95
² need >= 4 samples to detect a difference at alpha level 0.05