feat: consolidate 25 historical 2.x migrations into single end-of-2.7 schema

Generated via `doctrine:migrations:diff --formatted` against an empty test
DB with 25 latest-2.x migrations applied. The diff command (rather than
`dump-schema`) is used because dump-schema in doctrine/migrations 3.7
omits foreign key constraints from the generated migration; diff produces
a complete schema including all 96 FK clauses.

The `LegacyTemplateColumnsSchemaListener` was active during generation,
so the consolidated migration creates `template.icon`, `template.resources`,
and `template.description` even though the 3.0 entity no longer maps them.
This keeps fresh installs and 2.x → 3.0 upgraders symmetric — both end up
with the columns — so the deferred drop migration in 3.1 runs uniformly.

Also removes the previously 3.0-only `Version20250815092648` (template
column drop), which is deferred to 3.1 together with the listener.

Verified end-to-end:
- Fresh install: drop DB → migrate → schema:validate exits 0
- Upgrade from 2.7: 25 latest-2.x applied → swap files → rollup → status
  shows 1 executed / 1 available / 0 unavailable; schema:validate exits 0

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: turegjorup