feat: ai hashtags for posts

[gautamtayal1]

What kind of change does this PR introduce?

Feature: This PR adds AI-powered hashtag generation for social media posts.

Why was this change needed?

Picked up from Product Roadmap

Other Information

• New AiHashtag component that uses OpenAI to generate platform-specific hashtags based on post content.
• Backend endpoint and OpenAI service for hashtag suggestions.
• Hashtags are stored per-post in the database and appended to the message at posting time
• Integrated into the post creation modal with per-platform hashtag management
• Covers all integrated platforms.

Video

Screen.Recording.2026-03-02.at.9.40.43.PM_compressed.mp4

Checklist:

Put a "X" in the boxes below to indicate you have followed the checklist;

• I have read the CONTRIBUTING guide.
• I checked that there were not similar issues or PRs already open for this.
• This PR fixes just ONE issue (do not include multiple issues or types of change in the same PR) For example, don't try and fix a UI issue and include new dependencies in the same PR.

[vercel]

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[gautamtayal1]

@nevo-david @egelhaus just checking in on this PR - happy to make any changes if needed.