chore(deps): bump deps

fix: add per-provider request validation

Add Validate(Request) to the Poster interface and implement it for Mastodon, Twitter and Bluesky to enforce platform
length limits (character/grapheme checks). Dispatch now validates all posters before sending any posts, prints
validation failures, and returns a joined error to prevent partial posting. Add github.com/rivo/uniseg for grapheme
counting.

fix: append link to status text in Mastodon and Twitter posts

fix: bluesky not link-afying links

Update README.md

chore: add initial code