refactor: migrate from @tanstack/solid-db to standard @tanstack/solid-query

[nakatanakatana]

Summary

• Replaced the beta @tanstack/solid-db and @tanstack/query-db-collection state management with standard @tanstack/solid-query queries/mutations and pure TypeScript selectors.
• Rewrote the selectors to use standard SolidJS createMemo for reactivity, ensuring 100% type-safety and removing as any casts.
• Refactored UI components (FeedList, ItemList, AddFeedForm, ManageTagsModal, TagManagement, __root.tsx, url-rules.tsx, and block-rules.tsx) to subscribe to the new standard query structures.
• Added unit tests to verify database optimistic updates and fallback rollbacks on failure.

Test Plan

• Verified that all 87 node-based unit tests pass successfully.
• Ran the linter and TypeScript compilation check (npm run lint), which completed with zero errors and warnings.

[github-actions]

Code Metrics Report

	main (203082a)	#642 (7add131)	+/-
Coverage	55.1%	55.3%	+0.2%
Code to Test Ratio	1:1.3	1:1.3	+0.0
Test Execution Time	1m45s	1m20s	-25s

Details

  |                     | main (203082a) | #642 (7add131) |  +/-  |
  |---------------------|----------------|----------------|-------|
+ | Coverage            |          55.1% |          55.3% | +0.2% |
  |   Files             |            138 |            138 |     0 |
  |   Lines             |           9719 |           9720 |    +1 |
+ |   Covered           |           5356 |           5384 |   +28 |
+ | Code to Test Ratio  |          1:1.3 |          1:1.3 |  +0.0 |
  |   Code              |          12710 |          12459 |  -251 |
- |   Test              |          16797 |          16738 |   -59 |
+ | Test Execution Time |          1m45s |          1m20s |  -25s |

Code coverage of files in pull request scope (87.6% → 89.2%)

Files	Coverage	+/-	Status
frontend/src/components/AddFeedForm.tsx	94.5%	+0.5%	affected
frontend/src/components/FeedList.tsx	85.8%	+0.3%	affected
frontend/src/components/ItemDetailModal.tsx	92.0%	+0.0%	affected
frontend/src/components/ItemDetailRouteView.tsx	98.8%	+0.0%	affected
frontend/src/components/ItemList.tsx	88.9%	+0.6%	affected
frontend/src/components/ManageTagsModal.tsx	88.8%	+1.1%	affected
frontend/src/components/TagManagement.tsx	96.0%	-4.0%	affected
frontend/src/lib/block-db.ts	100.0%	+22.2%	affected
frontend/src/lib/feed-db.ts	53.0%	+1.2%	affected
frontend/src/lib/item-db.ts	96.8%	+26.5%	affected
frontend/src/lib/item-read-db.ts	98.1%	+13.2%	affected
frontend/src/lib/item-utils.ts	90.4%	-1.2%	affected
frontend/src/lib/queries/feed-queries.ts	85.2%	-8.1%	affected
frontend/src/lib/queries/item-queries.ts	97.2%	-2.8%	affected
frontend/src/mocks/handlers.ts	78.5%	-0.7%	affected
frontend/src/routes/__root.tsx	91.3%	+2.4%	affected
frontend/src/routes/_items.tsx	86.4%	+0.3%	affected
frontend/src/routes/block-rules.tsx	90.3%	-2.0%	affected
frontend/src/routes/url-rules.tsx	98.3%	-0.1%	affected
renovate.json	0.0%	0.0%	modified

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Reported by octocov