feat: add expiration column to aliases table

[wa0x6e]

Summary

Replaces the hardcoded 30-day expiry calculation with an explicit expiration timestamp column stored per-alias. Instead of computing expiry from created + 30 days at query time, the expiration is now set at creation time and checked directly. This enables future support for custom expiration periods and alias revocation (by setting expiration to a past value).

Changes

• ✨ Added expiration INT(11) NOT NULL column to aliases table schema
• ✨ Writer sets expiration = created + 30 days on alias creation
• ♻️ isExistingAlias() now checks expiration > NOW() instead of computing from created
• ♻️ Exported DEFAULT_ALIAS_EXPIRY_DAYS constant for reuse
• 🧪 Updated test fixtures with expiration field

Test plan

• Run yarn test:setup to recreate the test DB with new schema
• Verify all alias integration tests pass
• Verify expired aliases are still correctly rejected

Depends on #630

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Adds explicit per-alias expiration tracking by introducing an expiration timestamp column and updating alias validation logic to check it directly, replacing the previous “created + 30 days” query-time calculation.

Changes:

• Add expiration INT(11) NOT NULL (plus index) to the aliases table in the test schema.
• Set expiration at alias creation time (created + DEFAULT_ALIAS_EXPIRY_DAYS).
• Update isExistingAlias() to validate aliases via expiration > now, and export DEFAULT_ALIAS_EXPIRY_DAYS for reuse.
• Update alias SQL fixtures to include expiration.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
test/schema.sql	Adds expiration column and index to aliases table for the test DB schema.
test/fixtures/alias.ts	Updates fixtures to include expiration values.
src/writer/alias.ts	Sets expiration during alias creation using the shared default expiry constant.
src/helpers/alias.ts	Exports DEFAULT_ALIAS_EXPIRY_DAYS and updates isExistingAlias() to use expiration.

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