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/database/repos/share-alias/share-alias.repo.ts

@@ -0,0 +1,109 @@
+import { Injectable } from '@nestjs/common';
+import { InjectKysely } from 'nestjs-kysely';
+import { KyselyDB, KyselyTransaction } from '../../types/kysely.types';
+import { dbOrTx } from '../../utils';
+import {
+  InsertableShareAlias,
+  ShareAlias,
+} from '@docmost/db/types/entity.types';
+
+/**
+ * Repository for vanity share aliases (`/l/:alias`). An alias is a long-lived,
+ * workspace-scoped pointer to a page; retargeting is a single UPDATE of
+ * `page_id`. All lookups are workspace-scoped so a name in one workspace can
+ * never resolve a page in another.
+ */
+@Injectable()
+export class ShareAliasRepo {
+  constructor(@InjectKysely() private readonly db: KyselyDB) {}
+
+  private baseFields: Array<keyof ShareAlias> = [
+    'id',
+    'workspaceId',
+    'alias',
+    'pageId',
+    'creatorId',
+    'createdAt',
+    'updatedAt',
+  ];
+
+  /** Resolve a (normalized) alias within a workspace, or undefined. */
+  async findByAliasAndWorkspace(
+    alias: string,
+    workspaceId: string,
+    trx?: KyselyTransaction,
+  ): Promise<ShareAlias | undefined> {
+    return dbOrTx(this.db, trx)
+      .selectFrom('shareAliases')
+      .select(this.baseFields)
+      .where('alias', '=', alias)
+      .where('workspaceId', '=', workspaceId)
+      .executeTakeFirst();
+  }
+
+  /** The alias currently pointing at a page (for the share modal). */
+  async findByPageId(
+    pageId: string,
+    workspaceId: string,
+    trx?: KyselyTransaction,
+  ): Promise<ShareAlias | undefined> {
+    return dbOrTx(this.db, trx)
+      .selectFrom('shareAliases')
+      .select(this.baseFields)
+      .where('pageId', '=', pageId)
+      .where('workspaceId', '=', workspaceId)
+      .executeTakeFirst();
+  }
+
+  async findById(
+    id: string,
+    workspaceId: string,
+    trx?: KyselyTransaction,
+  ): Promise<ShareAlias | undefined> {
+    return dbOrTx(this.db, trx)
+      .selectFrom('shareAliases')
+      .select(this.baseFields)
+      .where('id', '=', id)
+      .where('workspaceId', '=', workspaceId)
+      .executeTakeFirst();
+  }
+
+  async insert(
+    insertable: InsertableShareAlias,
+    trx?: KyselyTransaction,
+  ): Promise<ShareAlias> {
+    return dbOrTx(this.db, trx)
+      .insertInto('shareAliases')
+      .values(insertable)
+      .returning(this.baseFields)
+      .executeTakeFirst();
+  }
+
+  /** Retarget an existing alias to a new page (the "swap" operation). */
+  async updatePageId(
+    id: string,
+    pageId: string,
+    workspaceId: string,
+    trx?: KyselyTransaction,
+  ): Promise<ShareAlias> {
+    return dbOrTx(this.db, trx)
+      .updateTable('shareAliases')
+      .set({ pageId, updatedAt: new Date() })
+      .where('id', '=', id)
+      .where('workspaceId', '=', workspaceId)
+      .returning(this.baseFields)
+      .executeTakeFirst();
+  }
+
+  async delete(
+    id: string,
+    workspaceId: string,
+    trx?: KyselyTransaction,
+  ): Promise<void> {
+    await dbOrTx(this.db, trx)
+      .deleteFrom('shareAliases')
+      .where('id', '=', id)
+      .where('workspaceId', '=', workspaceId)
+      .execute();
+  }
+}