[DOP-33859] Fix case-insensitive fetch by name

[dolfinus]

Change Summary

Make filtering, sorting and locking by lowercase Dataset.name, Job.name, Tag.name, TagValue.value - all of these have lowercase unique index.

Related issue number

Checklist

• Commit message and PR title is comprehensive
• Keep the change as small as possible
• Unit and integration tests for the changes exist
• Tests pass on CI and coverage does not decrease
• Documentation reflects the changes where applicable
• mddocs/docs/changelog/next_release/<pull request or issue id>.<change type>.md file added describing change
  (see CONTRIBUTING.rst for details.)
• My PR is ready to review.

[github-actions]

Coverage Report •

File	Stmts	Miss	Branch	BrPart	Cover	Missing
data_rentgen/db/repositories
dataset.py	79	0	22	2	98%	110->116, 116->118
job.py	109	0	32	2	99%	258->264, 264->266
run.py	134	29	48	13	77%	189->195, 285–286, 288–289, 291, 293, 301, 304–305, 307–308, 315–316, 319–322, 325–326, 329, 346–348, 356, 375–377, 379–380
user.py	32	1	4	0	97%	60
data_rentgen/server/services
dataset.py	21	1	0	0	95%	38
job.py	71	3	14	0	96%	83, 134, 231
TOTAL	7741	518	1328	217	92%