fix(postgres): Store capacities with finer prefix

[peterdudfield]

Update capacityToValueMultiplier to use 10's not 10^3's. This means we can get atleast 4.s.f.

I needed to remove a constraint in the sql code too

Example:
Before 32768 would get rounded to 33 x 10^3, and now it goes rounded to 3277 x 10^1

This helps fix #71

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• Have you written new tests for your changes?.
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• Have you successfully run make gen with your changes locally?
• Have you successfully run make test with your changes locally?

[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":"2025-11-26T17:38:06Z","message":"Running migrations"}
goos: linux
goarch: amd64
pkg: github.com/openclimatefix/data-platform/internal/server/postgres
cpu: AMD EPYC 7763 64-Core Processor                
BenchmarkPostgresClient/6144000/GetForecastAsTimeseries-4         	     151	   7602875 ns/op
BenchmarkPostgresClient/6144000/GetForecastAtTimestamp-4          	      38	  28892374 ns/op
BenchmarkPostgresClient/6144000/GetObservationsAsTimeseries-4     	     883	   1261007 ns/op
BenchmarkPostgresClient/6144000/CreateForecast-4                  	     258	   4246921 ns/op
PASS
ok  	github.com/openclimatefix/data-platform/internal/server/postgres	189.983s
?   	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-capacity-to-value-multiplier.txt │
                                                     │     sec/op     │     sec/op      vs base                │
PostgresClient/6144000/GetForecastAsTimeseries-4         4.826m ± ∞ ¹     7.603m ± ∞ ¹       ~ (p=1.000 n=1) ²
PostgresClient/6144000/GetForecastAtTimestamp-4         105.00m ± ∞ ¹     28.89m ± ∞ ¹       ~ (p=1.000 n=1) ²
PostgresClient/6144000/GetObservationsAsTimeseries-4     1.307m ± ∞ ¹     1.261m ± ∞ ¹       ~ (p=1.000 n=1) ²
PostgresClient/6144000/CreateForecast-4                  2.612m ± ∞ ¹     4.247m ± ∞ ¹       ~ (p=1.000 n=1) ²
geomean                                                  6.449m           5.857m        -9.19%
¹ need >= 6 samples for confidence interval at level 0.95
² need >= 4 samples to detect a difference at alpha level 0.05

[devsjc]

Looks good other than potentially some more test cases. I think there's probably still a discussion to be had around whether it's worth using NUMERIC/BIGINT here - if this is something we're likely to rub up against a lot; I don't think it would be too big of a hit since we're not doing much calculation with this value in the database anyway.

[devsjc]

Is it worth adding in those cases you were seeing that caused this ticket in the first place?

[peterdudfield]

The bottom three are, unless ive missed one

[devsjc]

I'm going to close this in favour of #92