[docs]doc: fix typos and grammar in docs and AccountController

[zhehenlu]

What's changed?

• Typo fixes (Commit 1)

  • Blog 2024-07-27-new-committer.md: internel→internet, monifying→modifying, fascinate→fascinated, at lease→at least, Therefor→Therefore
  • Portuguese alert doc alertmanager.pt-BR.md: use half-width period after HertzBeat
  • AI prompt system-message.st: heirarchy→hierarchy

• Grammar and wording consistency (Commit 2)

  • Docs: docker-deploy (due creating→due to creating), postgresql-change (a RDBMS→an RDBMS, allow→allows, skip instruction), mysql-change (MYSQL→MySQL, allow→allows), victoria-metrics-init (an VictoriaMetrics→a VictoriaMetrics), introduce (Alarm Threshold are→Alarm Thresholds are), across home/docs and versioned_docs 1.6.x/1.7.x/1.8.0
  • Code: AccountController — "Email already exist"→"Email already exists", and spacing after if / around = for style consistency

Checklist

• I have read the Contributing Guide
• I have written the necessary doc or comment.
• N/A for unit tests (doc/copy changes only; no logic change)

Add or update API

• N/A (no API changes)