[ONIX V18.36C-C8.2] Harden MCP-Notion Git newline and secret-ignore policy

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Summary

ONIX V18.36C-C8.2 applies repository hygiene hardening to the MCP-Notion working tree.

Changes

• Adds .env, .env.*, and *.bak* to .gitignore.
• Adds .gitattributes with LF normalization:
  • * text=auto eol=lf
  • *.json text eol=lf
• Restores package-lock.json to the upstream HEAD state.
• No dependency versions or application source code are intentionally changed.
• No credentials or secrets are introduced by this change.

Validation

• Local worktree clean.
• Index clean.
• package-lock.json verified clean against HEAD.
• Targeted secret scan: 0 hits.
• Commit scope verified: .gitignore and .gitattributes.
• Source fork commit:
  1bf2a0532860f66ba5c2c1cdbcba2e2942e849df

Scope

This PR is limited to repository hygiene and newline/secret-ignore policy.

Upstream main was not directly modified by ONIX.

Ref: ONIX V18.36C-C8.2