Sub-solutions filled from Joe's 39 workbooks; dummy assets wired

- Joe's 39 "- Completed" workbooks applied to all 39 sub-solution pages
  (#467-#515); both workbook inboxes are now gitignored and the tracked
  test workbooks untracked - filled deliveries live in the Nextcloud
- new Import\ProductFamilyAliases: the workbooks reference product
  FAMILIES in the product slots; 11 labels map to a representative
  product, consulted by BOTH importers after the exact title match and
  reported as "-> family alias"
- flip-card icons: dummy SVGs fileadmin/icons/flow/<name>.svg for Joe's
  10-name vocabulary, attached by the new attachIconFile() through the
  shared idempotent attachFalFile() (extracted from attachUrlFile);
  real icons later REPLACE those files in the Filelist (same sys_file
  uid), every card follows without a re-import
- image slots: numbered grey placeholders per page and slot
  (fileadmin/placeholders/pages/<pid>-NN.png, the id rendered into the
  image; generic grey as fallback). An existing reference is never
  overwritten; a real URL on re-import swaps the placeholder away
- page properties per sub-solution: og/twitter title + description
  mirror the SEO fields, canonical_link points at the page itself,
  abstract derived from the intro copy (~300 chars, word boundary),
  keywords from the curated PAGE_KEYWORDS set
- spec head-matter fix rides along (version table was stuck at 1.21,
  real state 1.23)

Open afterwards: 3 missing Datapath stories + re-apply, quotes on 16
story records (list to Joe), slug slash on page 467.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.gitignore

@@ -129,3 +129,7 @@ CLAUDE.local.md
 migrations/products_xlsx/*
 !migrations/products_xlsx/manifest.json
 /daten.md
+
+# Workbook inboxes: filled customer/agency workbooks live in the Nextcloud
+migrations/submarkets_xlsx_in/*
+migrations/subsolutions_xlsx_in/*