feat: add alias support for short URLs

[viganogabriele]

Summary

• New url_aliases table: each URL can have any number of alternate short codes that redirect to the same destination. Aliases resolve exactly like the primary code (getUrlByShortCode/redirect matches either), and urls.click_count stays the aggregate total across the primary code + all aliases (atomically incremented alongside the alias's own counter), while each alias also tracks its own click_count/last_clicked_at.
• Create dialog: alias chip input alongside the existing short-code field.
• Edit dialog: the short code is now editable (rename), rejecting collisions with any other URL's code/alias, and pointing the user at "promote" if they try to rename onto their own alias instead.
• New "Manage aliases" dialog (reachable via a button on each row, plus a click-count badge when aliases exist): add/remove aliases and see per-route click stats, with a "promote to primary" action per alias (swaps which code is primary; the demoted primary becomes a new alias, carrying over its derived direct-click history).
• New REST endpoints: POST/DELETE /urls/:shortCode/aliases, POST /urls/:shortCode/aliases/:aliasCode/promote, GET /urls/:shortCode/alias-stats; createUrl/updateUrl bodies gain aliases: string[].

Scope decisions

• No merge-on-collision: vigab.cc's version, when an alias collides with an existing primary short code, merges the two URLs (transferring click history, tags, other aliases) into one. That's complex, edge-case-heavy behavior that also assumed the tags feature existed. This PR just rejects the collision with a clear error instead — simpler and safer for a first cut; the merge workflow could be a follow-up if PoliNetwork wants it.
• No analytics-scope remapping on promote: vigab.cc's promote also re-routes detailed per-scope analytics rows. This repo's analytics PR (feat: add privacy-preserving click analytics and a /privacy page #29) is intentionally independent of this one, so promote here only touches url_aliases/urls — no analytics coupling.
• Kept independent of feat: add tagging system with color-coded badges #28 (tags) and feat: add privacy-preserving click analytics and a /privacy page #29 (analytics) by design, same as those two are independent of each other — avoids a deep PR stack. All three build on test: add vitest + pg-mem test infrastructure #27 (test infra) only.

Test plan

• pnpm test — 15 tests pass (alias CRUD, collision rejection, rename, promote with click-history transfer, reconcile-on-update)
• pnpm check (biome) passes
• pnpm build succeeds
• Manual: create a URL with aliases, visit an alias URL and confirm it redirects and increments clicks, rename the primary code, add/remove/promote aliases from the "Manage aliases" dialog

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📥 Commits

Reviewing files that changed from the base of the PR and between 8fb680c and 0159cfd.

⛔ Files ignored due to path filters (1)

• pnpm-lock.yaml is excluded by !**/pnpm-lock.yaml

📒 Files selected for processing (17)

• package.json
• src/app/api/[...ts-rest]/route.ts
• src/components/alias-stats-dialog.tsx
• src/components/create-url-dialog.tsx
• src/components/dashboard.tsx
• src/components/edit-url-dialog.tsx
• src/components/ui/badge.tsx
• src/components/url-record-row.tsx
• src/lib/actions.ts
• src/lib/contract.ts
• src/lib/db.ts
• src/lib/schemas.ts
• src/lib/url-service.test.ts
• src/lib/url-service.ts
• src/lib/utils.ts
• src/lib/validations.ts
• vitest.config.ts

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