fix(blog): tone down exclamation marks in May update post

[dobby-coder]

Closes #184.

The May update blogpost (`src/content/blog/postguard-may-update.svx`) contained four exclamation marks in body copy, which read as overly excited for a recap post. This change converts three of them to periods and keeps the closing line's exclamation as a single warm flourish.

Changes

Sentence	Before	After
Procolix thanks	`...grateful for that!`	`...grateful for that.`
Business launch	`...launched PostGuard for Business!`	`...launched PostGuard for Business.`
Add-ons CTA	`Check it out at https://postguard.eu/addons!\`	`Check it out at https://postguard.eu/addons.\`
Closing line	`...how far we've come!`	(unchanged)

Verification

• `npm run build` succeeds; rendered HTML in `build/blog/postguard-may-update/index.html` confirms the three sentences now end with periods.

Reviewer quickstart

`git fetch origin && git checkout fix/issue-184-tone-down-exclamations && npm install --legacy-peer-deps && npm run dev`

[dobby-coder]

Superseded by #202 (consolidation per encryption4all/dobby#53). Closing to keep the queue tidy.