fix(web): field-mapping + fragile-hx-vals sweep across profile and library surfaces

Field-by-field audit of the profile surface (set → save → reopen →
read back, driven through the emulator browser via CDP):

- getTemplateUserWithTheme (every SSR page + the /profile self-edit
  form) never mapped FirstName/LastName/CreatedAt — stored names
  rendered as empty inputs. Now mapped (timezone was already mapped).
- Admin profile-modal Timezone mapping fixed earlier this round held:
  all seven fields verified set → 200 + HX-Refresh → reopen → correct
  values, DB cross-checked.
- Role promote/demote via the card select verified against the DB (the
  PUT answers HX-Refresh, so the page reload shows the new role).
- Admin password reset verified end-to-end: new password logs in, old
  one 401s, original restored.
- admin_library folder-remove hx-vals was string-concatenated JSON —
  a folder path containing a quote or backslash made it invalid and
  the remove button silently died under htmx 2 (the same class as the
  profile-save bug). Now built with json.Marshal behind the js:
  prefix. Verified the generated attribute on the live page.
- Other hx-vals/hx-headers sites audited: constants and uuids only
  (safe charset), left alone.

templates/admin_library.templ

@@ -307,7 +307,7 @@ templ LibraryPanel(user User, libraryID string, library LibraryData, folders []F
 							<button
 								class="icon-btn h-7 w-7 shrink-0"
 								hx-delete={ "/admin/library/" + libraryID + "/folders" }
-								hx-vals={ `{"folder_path": "` + folder.FolderPath + `"}` }
+								hx-vals={ hxValsFolderDelete(folder.FolderPath) }
 								hx-target={ "#library-panel-" + libraryID }
 								hx-swap="innerHTML"
 								hx-confirm="Remove this folder from the library?"