perf(front): drop Carbon and Doctrine Inflector from uncached page renders

[elcreator]

Summary

A cache-miss render of a page on a fresh install loaded Carbon and Doctrine Inflector although the page needs
neither. This PR removes both from the front-end path and seeds the default template the way the manager creates
new ones.

• upd(install) – the seeded Minimal Template now uses templatesource = 'db'. It was the only template in
  a fresh system on the legacy "Automatic (a matching file wins)" source; templates created in the manager already
  default to db. This is for consistency: the skipped view-file probes do not change render time measurably.
• fix(models) – SiteContent::toArray() no longer builds a Carbon instance for deletedon. The base
  soft-delete trait casts that column to datetime, so every uncached page loaded Carbon (~40 files) and
  [*deletedon*] rendered as 1970-01-01T00:00:00.000000Z instead of a Unix timestamp like every other date field.
  The array form now keeps the stored value; reading $doc->deletedon still returns Carbon.
• ref(models) – all 29 core models without $table now declare it. Without it, Eloquent pluralises the class
  name on the first query, which loads Doctrine Inflector (~20 files). Each name is exactly the one Eloquent derived
  before, so no query changes.

Measurements

Fresh SQLite install, PHP 8.3 with OPcache, Apache, guest request to the home page with the page cache off (200
requests per run):

	PHP files loaded	median
before	447	5.79–5.97 ms
after	381	5.21–5.45 ms

About 0.55 ms (~9%) per cache miss in the two quiet rounds; later rounds were too noisy to compare. Cached hits (~3
ms, 0 queries) are unaffected.

Behaviour change

toArray() / toJson() of a document now gives deletedon as an integer (0 when never deleted) instead of an
ISO string, matching createdon, editedon and the other date fields.

A subclass of a core model that does not set its own $table now inherits the parent's table instead of one
derived from the subclass name. Nothing shipped does this.

Tests

• DefaultSiteTemplateSeederTest – both install seeders seed templatesource = 'db'; the CI smoke check asserts
  the same on a real install.
• SiteContentDeletedOnArrayTest – integer deletedon in arrays, column order and other casts kept, attribute
  access still Carbon, an in-memory deletion time is arrayed as a timestamp, and (in a separate process) arraying a
  document does not load Carbon.
• ModelTableNamesTest – every core model declares its table, and the 29 new declarations equal Eloquent's derived
  names.

Unit suite: 1097 passed, 2 skipped. PHPStan: 0 errors, as before.