fix(discord): validate integer env values strictly

[aiirvizionz]

Summary

• require Discord integer environment values to use decimal digits only
• reject exponent, hexadecimal, signed, fractional, whitespace-padded, and unsafe values
• preserve existing safe fallback behavior for invalid configuration

Validation

• vitest run packages/bots/discord/src/index.test.ts (10 tests passed)
• tsc -p packages/bots/discord/tsconfig.json --noEmit
• git diff --check

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[github-actions]

🤖 Auto-rebase: The branch was rebased successfully locally but could not be pushed to the fork. Please enable 'Allow edits from maintainers' in the PR settings, or rebase manually: git fetch upstream master && git rebase upstream/master.

[github-actions]

🤖 Auto-rebase: The branch was rebased successfully locally but could not be pushed to the fork. Please enable 'Allow edits from maintainers' in the PR settings, or rebase manually: git fetch upstream master && git rebase upstream/master.