feat(share): custom /l/:alias pretty links (share_aliases table) (#205)

Add a retargetable, human-readable vanity link namespace /l/<alias> that
sits alongside the untouched /share/... routes.

- New share_aliases table (workspace-scoped, UNIQUE(workspace_id, alias),
  page_id nullable ON DELETE SET NULL so the address outlives its target).
- ShareAliasRepo + ShareAliasService (create / no-op / 409 reassign guard /
  availability / request-time readable-target resolution through the single
  existing share boundary).
- Public ShareAliasRedirectController (GET /l/:alias) issues a 302 (never 301,
  the target is mutable) to the canonical /share/:key/p/:slug page; unknown /
  dangling / no-longer-readable aliases serve the SPA index with no leak.
  'l/:alias' excluded from the global /api prefix.
- Authenticated ShareAliasController (set/remove/availability/for-page).
- Shared ASCII-only normalize/validate util (server + client copies).
- Client: Custom address block in the share modal (live normalize + debounced
  availability + copy + reassign confirmation dialog).
- Unit tests: util, repo SQL-shape, service semantics, migration/entity sanity
  (server jest) + client alias util (vitest).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/server/src/core/share/share-alias.util.spec.ts

@@ -0,0 +1,60 @@
+import { isValidShareAlias, normalizeShareAlias } from './share-alias.util';
+
+describe('normalizeShareAlias', () => {
+  it('lowercases and trims', () => {
+    expect(normalizeShareAlias('  HelloWorld  ')).toBe('helloworld');
+  });
+
+  it('converts spaces and underscores to single hyphens', () => {
+    expect(normalizeShareAlias('my cool   page')).toBe('my-cool-page');
+    expect(normalizeShareAlias('my_cool_page')).toBe('my-cool-page');
+  });
+
+  it('collapses repeated hyphens and trims edge hyphens', () => {
+    expect(normalizeShareAlias('--a---b--')).toBe('a-b');
+  });
+
+  it('handles null/undefined defensively', () => {
+    expect(normalizeShareAlias(undefined as unknown as string)).toBe('');
+  });
+});
+
+describe('isValidShareAlias', () => {
+  it('accepts ascii lowercase hyphen-separated slugs', () => {
+    expect(isValidShareAlias('hello')).toBe(true);
+    expect(isValidShareAlias('hello-world-2')).toBe(true);
+    expect(isValidShareAlias('a1')).toBe(true);
+  });
+
+  it('rejects too short / too long', () => {
+    expect(isValidShareAlias('a')).toBe(false);
+    expect(isValidShareAlias('a'.repeat(61))).toBe(false);
+    expect(isValidShareAlias('a'.repeat(60))).toBe(true);
+  });
+
+  it('rejects leading/trailing/double hyphens', () => {
+    expect(isValidShareAlias('-abc')).toBe(false);
+    expect(isValidShareAlias('abc-')).toBe(false);
+    expect(isValidShareAlias('a--b')).toBe(false);
+  });
+
+  it('rejects uppercase, cyrillic and other non-ascii', () => {
+    expect(isValidShareAlias('Hello')).toBe(false);
+    expect(isValidShareAlias('привет')).toBe(false);
+    expect(isValidShareAlias('a b')).toBe(false);
+    expect(isValidShareAlias('a_b')).toBe(false);
+    expect(isValidShareAlias('a.b')).toBe(false);
+  });
+
+  it('normalize + validate round-trips a messy input to a valid slug', () => {
+    const alias = normalizeShareAlias('  My  Cool_Page!! ');
+    // "!!" is not stripped by normalize (only case/separators), so the result
+    // still fails validation — the charset gate is intentionally separate.
+    expect(alias).toBe('my-cool-page!!');
+    expect(isValidShareAlias(alias)).toBe(false);
+
+    const ok = normalizeShareAlias('  My  Cool Page ');
+    expect(ok).toBe('my-cool-page');
+    expect(isValidShareAlias(ok)).toBe(true);
+  });
+});