fix(tree): panic in findCaseInsensitivePathRec with RedirectFixedPath (#4535)

* fix(tree): panic in findCaseInsensitivePathRec with RedirectFixedPath enabled

When RedirectFixedPath is enabled and a request doesn't match any route,
findCaseInsensitivePathRec panics with "invalid node type". This happens
because it accesses children[0] to find the wildcard child, but addChild()
keeps the wildcard child at the end of the array (not the beginning).

When a node has both static and wildcard children, children[0] is a static
node, so the switch on nType falls through to the default panic case.

The fix mirrors what getValue() already does correctly (line 483):
use children[len(children)-1] to access the wildcard child.

Fixes #2959

* Address review feedback: improve test assertions and prefer static routes in case-insensitive lookup

- Assert found=false for non-matching paths instead of only checking for panics
- Fix expected casing for case-insensitive static route match (/PREFIX/XXX -> /prefix/xxx)
- Update findCaseInsensitivePathRec to try static children before falling back to
  wildcard child, ensuring static routes win over param routes in case-insensitive matching

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Co-authored-by: Bo-Yi Wu <[email protected]>