feat: file blocks (#10)

Phase 3, part 2 (`docs/design.md`, "Next"): file blocks. Moderators block a file network-wide by its sha256, so a removed product can't come back under another name or catalog.

**Blocking**
- A file's page (Console → Blocks → a file) shows whether it's blocked and the products using it, so a moderator sees what a block removes before confirming ("Block and remove 2 products").
- Moderators reach it from a product's files (each has a Block link for them) or by pasting a sha256 into the Blocks tab, which also lists blocked files.
- Blocking a file:
  - removes every product with a revision using it. Each removal is audited as `product.remove` with the file, so creators are notified and can appeal it as before.
  - puts a `{type: "block", sha256}` change in the changes feed of every catalog hosting it, meaning: delete it whatever uses it. (t5de-catalog doesn't read the feed yet.)
  - refuses uploads with it from then on (409 `blocked`). Each attempt is audited as `file.blocked_upload` with the person and catalog, so moderators see who tried.
- Unblocking lets the file in again. The products it removed stay removed until a moderator restores them, one by one.
- Who: `product:remove` hub-wide (moderators and admins). The Blocks tab shows only for them.

**API**: `GET /api/v1/blocks`, and `GET`/`PUT`/`DELETE /api/v1/blocks/:sha256` (`docs/products.md`).

**Migration** `0013_file_blocks`: the `file_block` table, and a GIN index on revisions' file lists, so finding the products using a file doesn't scan every revision.

**Checks**
- 53 API tests pass. The new `blocks.test.ts` covers:
  - who may block
  - the preview of what a block removes
  - removal of every product using the file, across catalogs and creators
  - the changes feed, notifications and appeals
  - refused uploads and their audit entry
  - unblocking, and restoring a removed product afterwards
- Type checks pass.
- On a local hub, through the website's own forms:
  - the Block link on a product's files, for moderators only
  - the Blocks tab, for moderators only (404 for the creator)
  - the file's page, then blocking: the product is gone, its creator notified and offered Appeal
  - a re-upload through the catalog API: refused, and audited
  - unblocking, then Restore
  - Fixed along the way: an empty reason gave a generic "Some of that isn't right"; it now says "Give a reason."

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Phase 3, part 2 (`docs/design.md`, "Next"): file blocks. Moderators block a file network-wide by its sha256, so a removed product can't come back under another name or catalog.

**Blocking**
- A file's page (Console → Blocks → a file) shows whether it's blocked and the products using it, so a moderator sees what a block removes before confirming ("Block and remove 2 products").
- Moderators reach it from a product's files (each has a Block link for them) or by pasting a sha256 into the Blocks tab, which also lists blocked files.
- Blocking a file:
  - removes every product with a revision using it. Each removal is audited as `product.remove` with the file, so creators are notified and can appeal it as before.
  - puts a `{type: "block", sha256}` change in the changes feed of every catalog hosting it, meaning: delete it whatever uses it. (t5de-catalog doesn't read the feed yet.)
  - refuses uploads with it from then on (409 `blocked`). Each attempt is audited as `file.blocked_upload` with the person and catalog, so moderators see who tried.
- Unblocking lets the file in again. The products it removed stay removed until a moderator restores them, one by one.
- Who: `product:remove` hub-wide (moderators and admins). The Blocks tab shows only for them.

**API**: `GET /api/v1/blocks`, and `GET`/`PUT`/`DELETE /api/v1/blocks/:sha256` (`docs/products.md`).

**Migration** `0013_file_blocks`: the `file_block` table, and a GIN index on revisions' file lists, so finding the products using a file doesn't scan every revision.

**Checks**
- 53 API tests pass. The new `blocks.test.ts` covers:
  - who may block
  - the preview of what a block removes
  - removal of every product using the file, across catalogs and creators
  - the changes feed, notifications and appeals
  - refused uploads and their audit entry
  - unblocking, and restoring a removed product afterwards
- Type checks pass.
- On a local hub, through the website's own forms:
  - the Block link on a product's files, for moderators only
  - the Blocks tab, for moderators only (404 for the creator)
  - the file's page, then blocking: the product is gone, its creator notified and offered Appeal
  - a re-upload through the catalog API: refused, and audited
  - unblocking, then Restore
  - Fixed along the way: an empty reason gave a generic "Some of that isn't right"; it now says "Give a reason."

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: dhkatz <[email protected]>

apps/web/app/products/[id]/page.tsx

@@ -189,6 +189,7 @@ export default async function ProductPage({ params }: { params: Promise<{ id: st
                 stayOn={stayOn}
                 using={using === r.number}
                 mine={mine}
+                canBlock={permissions.includes("product:remove")}
               />
             ))}
           </ul>
@@ -212,6 +213,7 @@ function RevisionRow({
   stayOn,
   using,
   mine,
+  canBlock,
 }: {
   id: string;
   revision: Revision;
@@ -220,6 +222,8 @@ function RevisionRow({
   stayOn: number | null;
   using: boolean;
   mine: boolean;
+  /** Moderators: each file links to blocking it. */
+  canBlock: boolean;
 }) {
   const facts = [
     formatSize(r.size),
@@ -247,6 +251,11 @@ function RevisionRow({
             <li key={f.name} className="flex gap-3">
               <span className="min-w-0 flex-1 truncate">{f.name}</span>
               <span className="text-muted-foreground tabular-nums">{formatSize(f.size)}</span>
+              {canBlock && (
+                <Link href={`/console/blocks/${f.sha256}`} className="text-muted-foreground underline-offset-4 hover:text-foreground hover:underline">
+                  Block
+                </Link>
+              )}
             </li>
           ))}
         </ul>