feat: add language support and tests for English and Chinese seed data

- Introduced a new package `seedlang` to handle language parsing and constants for English and Chinese.
- Updated `Init` functions across various modules (kb, quickreply, skill, tag) to accept a language parameter.
- Implemented English seed data for FAQs, quick replies, skills, and tags, ensuring no Chinese text is present in English data.
- Added tests to verify that English seed data does not contain Chinese characters.
- Removed outdated README file from the kb test data directory.
- Created new test files for channel and kb to validate the absence of Chinese text in English seed data.

README.md

@@ -206,7 +206,8 @@ make check          # run Go tests, frontend typecheck, and lint
 make generator      # run code generation
 make enums          # generate frontend enums
 make migration      # run migrations
-make testdata       # initialize demo/test data
+make testdata       # initialize Chinese demo/test data
+make testdata TESTDATA_LANG=en  # initialize English demo/test data
 ```
 
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