docs: add SSL/TLS database connection guide and document missing env vars (#2377)

* docs: add SSL/TLS database connection guide and document missing env vars

- Add comprehensive SSL/TLS Connection section to database infrastructure guide
  covering DATABASE_SSL_* env vars (auto-wired by MySQLFactory), DSN query
  parameter alternative, cert generation, AWS RDS example, and verification
- Document two previously undocumented database env vars:
  DATABASE_PERSISTENT_CONNECTION and DATABASE_PROTOCOL_COMPRESSION
- Fix environment variables table descriptions to clarify that
  DATABASE_SSL_* vars are automatically applied by MySQLFactory
- Update deployment-helper docs and troubleshooting with accurate links

* Apply suggestions from code review

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

* docs: remove incorrect SSL DSN query parameter docs from database guide

SSL query parameters (sslrootcert, sslcert, sslkey, etc.) do not work
via DATABASE_URL for MySQL in PHP. DATABASE_SSL_* env vars are the
only supported approach.

* docs: document DATABASE_SSL_CA=true workaround for forcing SSL without CA

* docs: apply markdown lint fixes

* fix/link-and-tables

* docs: expand DB connection options with use cases and trade-offs

* docs: use env var names instead of internal constants in headings

* docs: remove redundant connection options intro section

* docs: apply markdown lint fixes (blank lines after bold headings)

* adjust/typical-syntax

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Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Micha <m.hobert@shopware.com>

Author: 3 people