chore: configure dependency minimum release age / cooldown (#216)

Adds a minimum release age ("cooldown") to this repo's package-manager
configuration so newly published dependency versions wait ~7 days before they
can be adopted. This reduces exposure to compromised or unstable packages that
are caught and unpublished shortly after release.

Applied per package manager found in the repo:
- Dependabot (.github/dependabot.yml): cooldown.default-days: 7 per ecosystem
- pnpm (pnpm-workspace.yaml): minimumReleaseAge: 10080 (minutes)
- npm (.npmrc): min-release-age=7 (days)
- yarn (.yarnrc.yml): npmMinimalAgeGate: "7d"
- bun (bunfig.toml): minimumReleaseAge = 604800 (seconds)
- uv (pyproject.toml): exclude-newer = "7 days"

Generated and verified with semgrep (package_managers.* rules); the check passes
after this change.

Author: Piccirello

pnpm-workspace.yaml

@@ -2,3 +2,5 @@ packages:
   - 'src/PostHog'
   - 'src/PostHog.AspNetCore'
   - 'src/PostHog.AI'
+
+minimumReleaseAge: 10080