Add FNV-1a hash algorithm implementation

[rodrigobnogueira]

Description

Implements the FNV-1a (Fowler-Noll-Vo) hash algorithm with both 32-bit and 64-bit variants. FNV-1a is a fast, non-cryptographic hash function widely used in hash tables, bloom filters, and caches.

Changes

• Added hashes/fnv.py with complete implementation of:
  • fnv1a_32(): 32-bit variant
  • fnv1a_64(): 64-bit variant
• Simple XOR-multiply algorithm
• 22 comprehensive doctests (11 per variant)
• Full type hints and English documentation

Features

• Extremely simple and fast implementation
• Excellent distribution properties
• Used in popular systems (hash tables, databases)
• Complements existing hash algorithms (CRC32, MD5, SHA)

Real-world Applications

• Hash tables and hash maps
• Bloom filters
• Database indexing
• Cache implementations
• Checksums for data integrity

References

• https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
• http://www.isthe.com/chongo/tech/comp/fnv/

Testing

• All 22 doctests pass
• Passes ruff linting
• Passes mypy type checking
• Tested with various inputs including edge cases

Checklist

• [x] I have read and followed the contributing guidelines
• [x] This pull request is not a duplicate
• [x] The algorithm is implemented from scratch
• [x] The code follows the repository style
• [x] I have read CONTRIBUTING.md
• [x] This pull request is all my own work -- I have not plagiarized
• [x] I know that pull requests will not be merged if they fail the automated tests
• [x] This PR only changes one algorithm file
• [x] All new Python files are placed inside an existing directory (hashes/)
• [x] All filenames are in all lowercase characters with no spaces or dashes
• [x] All functions and variable names follow Python naming conventions
• [x] All function parameters and return values are annotated with Python type hints
• [x] All functions have doctests that pass the automated testing
• [x] All new algorithms include at least one URL that points to Wikipedia or another similar explanation