Remove outdated migration documentation and regenerate template after
script tag cleanup.
Changes:
- Delete ECHO_V5_MIGRATION.md: Obsolete migration plan, superseded by
ESBUILD_MIGRATION_PLAN.md
- Delete esbuild-setup.md: Incomplete setup document, replaced by
comprehensive migration plan
- Regenerate templates/collections_templ.go: Remove collections.js
script tag (now using main.js bundle)
Template update:
- Removed <script src="/static/collections.js"> from template
- Now uses single main.js bundle (ESBuild output)
- Line number adjustments in generated Go code
Cleanup of obsolete documentation as part of ESBuild migration.