events: Integer returns the documented range error instead of a wrong number

[lenamonj]

DynamoDBAttributeValue.Integer documents that a value outside int64 comes back as the maximum magnitude int64 of the matching sign with err.Err = ErrRange. strconv.ParseInt returns exactly that, but Integer treats every parse error as a decimal string and retries with ParseFloat, which succeeds and drops the error: on amd64 NewNumberAttribute("99999999999999999999").Integer() returns -9223372036854775808, nil, the wrong sign and no error. DynamoDB numbers carry up to 38 digits, so this is ordinary content.

The change keeps the ParseFloat fallback for syntax errors only and saturates with ErrRange when a parsed float is outside int64 as well; "123.45" still returns 123. The new test fails on main and passes with the change. go test -race ./events/ and golangci-lint v2.13.1 are clean.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 82.38%. Comparing base (6800157) to head (7a9ecb2).

Files with missing lines	Patch %	Lines
events/attributevalue.go	88.88%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #640   +/-   ##
=======================================
  Coverage   82.38%   82.38%           
=======================================
  Files          36       36           
  Lines        1419     1425    +6     
=======================================
+ Hits         1169     1174    +5     
- Misses        247      248    +1     
  Partials        3        3           

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