Turn the image library into a file library, with a per-blog upload limit

Bloggers want to attach PDFs, archives, audio and other files to posts,
not only images. The Images tab becomes Files: any type is accepted,
listed by kind with search, paging, rename and multi-file upload, and the
editor's paste/drop/"Insert file" takes anything (images are shown,
everything else becomes a link). The default limit goes from 5 to 10 MB
and the superadmin can override it per blog from /admin/.

Files stay in Postgres so one pg_dump is still the whole blog. The bytea
column is STORAGE EXTERNAL and /media streams it in substring() slices,
so serving never holds a whole file in memory whatever limit a blog gets.

Serving any type on the root domain, which carries the session cookie,
needs a policy: uploads are typed by sniffing (the extension may only
refine a generic sniff to an allowlisted type) and only images, PDF,
plain text, audio and video render inline; HTML, SVG, XML, scripts,
archives and binaries always go out as application/octet-stream with
Content-Disposition: attachment.

The body cap moves out of requireAuth into guardPOST, which runs after
withBlog has resolved the blog and so knows its limit.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Sd8UPWrvyYCLj97JexNw3A

1 files changed, 7 insertions, 2 deletions

diff --git a/cmd/blogspace/seed.go b/cmd/blogspace/seed.go
index f69a774..05c54f8 100644
--- a/cmd/blogspace/seed.go
+++ b/cmd/blogspace/seed.go
@@ -77,7 +77,12 @@ func seed(ctx context.Context, cfg *config.Config, st *store.Store) error {
 	if err := png.Encode(&buf, img); err != nil {
 		return err
 	}
-	bg, err := bs.CreateImage(ctx, "gradient.png", "image/png", buf.Bytes())
+	bg, err := bs.CreateFile(ctx, "gradient.png", "image/png", "image", buf.Bytes())
+	if err != nil {
+		return err
+	}
+	// and a plain text file, so the Files tab shows more than images
+	notes, err := bs.CreateFile(ctx, "notes.txt", "text/plain", "document", []byte("Reading list:\n- The Go Programming Language\n- Practical Vim\n"))
 	if err != nil {
 		return err
 	}
@@ -107,7 +112,7 @@ func seed(ctx context.Context, cfg *config.Config, st *store.Store) error {
 		}
 	}
 	posts := []struct{ page, title, body string }{
-		{"home", "Welcome to my corner of the web", "This is the **first post**. It lives on the home page.\n\nThings I plan to write about:\n\n- tomatoes\n- Go\n- the occasional recipe\n\n![gradient](/media/" + bg.ID.String() + ")\n\nThat image above was uploaded through the dashboard."},
+		{"home", "Welcome to my corner of the web", "This is the **first post**. It lives on the home page.\n\nThings I plan to write about:\n\n- tomatoes\n- Go\n- the occasional recipe\n\n![gradient](/media/" + bg.ID.String() + ")\n\nThat image above was uploaded through the dashboard, and here is a file to download: [notes.txt](/media/" + notes.ID.String() + ")."},
 		{"home", "Why I still like plain HTML", "No frameworks, no build step. Just `<p>` tags and a stylesheet.\n\n> Simplicity is prerequisite for reliability. — Dijkstra\n\n```go\nfunc main() {\n\tfmt.Println(\"hello\")\n}\n```"},
 		{"news", "Site is up", "The blog is live. Expect sporadic updates."},
 		{"news", "Tomato season", "First ripe tomato of the year! Table for the record:\n\n| Variety | Days |\n|---|---|\n| Cherry | 62 |\n| Beefsteak | 85 |"},