fix(sql): Remove retention policy from partman

[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

Partman previously had the retention policy set to one month, but we
want to be able to query data that is older than that. This resets
partman to have no retention policy, and reattaches and detached
partitions from the affected tables.

[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":"2026-05-18T17:26:11Z","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         	      62	  18483449 ns/op
BenchmarkPostgresClient/small/GetForecastAtTimestamp-4          	     280	   3945410 ns/op
BenchmarkPostgresClient/small/GetObservationsAsTimeseries-4     	    1064	   1063667 ns/op
BenchmarkPostgresClient/small/CreateForecast-4                  	      96	  11970752 ns/op
BenchmarkPostgresClient/small/StreamForecastData-4              	      12	  84265553 ns/op
PASS
ok  	github.com/openclimatefix/data-platform/internal/server/postgres	65.732s
?   	github.com/openclimatefix/data-platform/internal/server/postgres/gen	[no test files]