⚡ refactor: Optimize & Standardize Tokenizer Usage (#10777)

* refactor: Token Limit Processing with Enhanced Efficiency

- Added a new test suite for `processTextWithTokenLimit`, ensuring comprehensive coverage of various scenarios including under, at, and exceeding token limits.
- Refactored the `processTextWithTokenLimit` function to utilize a ratio-based estimation method, significantly reducing the number of token counting function calls compared to the previous binary search approach.
- Improved handling of edge cases and variable token density, ensuring accurate truncation and performance across diverse text inputs.
- Included direct comparisons with the old implementation to validate correctness and efficiency improvements.

* refactor: Remove Tokenizer Route and Related References

- Deleted the tokenizer route from the server and removed its references from the routes index and server files, streamlining the API structure.
- This change simplifies the routing configuration by eliminating unused endpoints.

* refactor: Migrate countTokens Utility to API Module

- Removed the local countTokens utility and integrated it into the @librechat/api module for centralized access.
- Updated various files to reference the new countTokens import from the API module, ensuring consistent usage across the application.
- Cleaned up unused references and imports related to the previous countTokens implementation.

* refactor: Centralize escapeRegExp Utility in API Module

- Moved the escapeRegExp function from local utility files to the @librechat/api module for consistent usage across the application.
- Updated imports in various files to reference the new centralized escapeRegExp function, ensuring cleaner code and reducing redundancy.
- Removed duplicate implementations of escapeRegExp from multiple files, streamlining the codebase.

* refactor: Enhance Token Counting Flexibility in Text Processing

- Updated the `processTextWithTokenLimit` function to accept both synchronous and asynchronous token counting functions, improving its versatility.
- Introduced a new `TokenCountFn` type to define the token counting function signature.
- Added comprehensive tests to validate the behavior of `processTextWithTokenLimit` with both sync and async token counting functions, ensuring consistent results.
- Implemented a wrapper to track call counts for the `countTokens` function, optimizing performance and reducing unnecessary calls.
- Enhanced existing tests to compare the performance of the new implementation against the old one, demonstrating significant improvements in efficiency.

* chore: documentation for Truncation Safety Buffer in Token Processing

- Added a safety buffer multiplier to the character position estimates during text truncation to prevent overshooting token limits.
- Updated the `processTextWithTokenLimit` function to utilize the new `TRUNCATION_SAFETY_BUFFER` constant, enhancing the accuracy of token limit processing.
- Improved documentation to clarify the rationale behind the buffer and its impact on performance and efficiency in token counting.

api/server/routes/index.js

@@ -1,7 +1,6 @@
 const accessPermissions = require('./accessPermissions');
 const assistants = require('./assistants');
 const categories = require('./categories');
-const tokenizer = require('./tokenizer');
 const endpoints = require('./endpoints');
 const staticRoute = require('./static');
 const messages = require('./messages');
@@ -53,7 +52,6 @@ module.exports = {
   messages,
   memories,
   endpoints,
-  tokenizer,
   assistants,
   categories,
   staticRoute,