feat(frontend): migrate react-router v5 to TanStack Router

[msyavuz]

SUMMARY

Upgrade react-router to latest tanstack router version

• Replace BrowserRouter/Switch/Route with a TanStack route tree built from the existing routes.tsx table; route chunks preload on link hover/focus (defaultPreload: 'intent') via fire-and-forget loaders
• Custom raw-string search param codec so rison payloads round-trip through the router untouched
• TanstackRouterAdapter replaces ReactRouter5Adapter for use-query-params
• StandaloneRouter (RouterContextProvider-based, synchronous mount) hosts the menu entry on Flask pages and component tests
• pushAppHref/replaceAppHref helpers restore v5's basename-prefixing semantics for raw href navigation
• useUnsavedChangesPrompt now uses useBlocker
• Migrate all 92 importing files; drop react-router-dom dependency

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 64.16%. Comparing base (f27424d) to head (4c233d9).
⚠️ Report is 25 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff            @@
##           master   #40971    +/-   ##
========================================
  Coverage   64.16%   64.16%            
========================================
  Files        2655     2655            
  Lines      143863   143682   -181     
  Branches    33181    33166    -15     
========================================
- Hits        92306    92199   -107     
+ Misses      49936    49859    -77     
- Partials     1621     1624     +3     

Flag	Coverage Δ
hive	39.44% <ø> (-0.02%)	⬇️
mysql	58.19% <ø> (+<0.01%)	⬆️
postgres	58.25% <ø> (+<0.01%)	⬆️
presto	41.03% <ø> (-0.02%)	⬇️
python	59.73% <ø> (+<0.01%)	⬆️
sqlite	57.87% <ø> (+<0.01%)	⬆️
unit	100.00% <ø> (ø)

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