inbound-antispam-panel: Inbound log, Why as a sheet; no Deny on a Postfix reject

Follows the two design commits before it (owner's decisions quoted
there).

Kit: a new component, Sheet / SheetRow (components.go), partials
sheet_tag and sheet (components.html), its rules in panel.css as in
theme.css, and its sample on the kit page next to status_tag. It is
the browser's popover: no script.

Inbound log: the Why column is gone; the decision tag opens a sheet
with who decided, then either the filter's verdict and its symbols one
a line (a detail the journal milter wrote) or the reply (a detail the
tailer read from mail.log - it starts with its code), and the subject
whole. The sheet's id is the journal row's. A row Postfix itself
refused no longer links to the filter lists.

Tests: the page fixture and view tests for the sheet's markup and
content (TestWhyRows), the link rule, three Deny and two Allow on the
mockup's six rows; e2e reads "Decided by" and "Reply" from the sheet
and wants no sender link on the refused row.

Seen: the fixture page with a sheet open, headless Edge at 1360 px -
the same as the accepted drawing.

Checked on the test server, uncommitted tree: go vet ./... ok,
go test ./... ok (22 packages), make e2e ok.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/web/view/components.go

@@ -105,6 +105,27 @@ type Tag struct {
 	Label  string
 }
 
+// Sheet is what does not fit a table row, opened over the page from the row's
+// tag (partials "sheet_tag" and "sheet"; used by the Inbound log, where it says
+// why a message was decided the way it was). It is the browser's own popover:
+// the tag is a button that names the sheet by ID, so ID is unique on the page.
+// Its content is a table of name and value.
+type Sheet struct {
+	ID    string
+	Tag   Tag
+	Title string
+	Rows  []SheetRow
+}
+
+// SheetRow is one name and its value in a sheet. A value of several lines is
+// one line each; Mono is for what is read as written - a reply, a list of
+// symbols.
+type SheetRow struct {
+	Label string
+	Lines []string
+	Mono  bool
+}
+
 // statusClass is the one mapping of status to Bulma tag classes — box 03 of the
 // kit page. A page passes the status it knows (a DKIM check says ok, a message
 // says deferred) and never picks a colour.