feat: 5 social media templates for bounty announcements (Bounty #829)

[liufang88789-ui]

Summary

Delivers 5 reusable social media templates for announcing bounties on X/Twitter, matching SolFoundry's dark theme + emerald/magenta forge aesthetic.

Deliverables

10 Files (5 templates × 2 sizes)

• Feed posts — (1080×1080px) — square X/Twitter feed
• Twitter cards — (1200×675px) — landscape link preview

Template Themes

Template	Headline	Badge Color
T1	NEW BOUNTY ALERT	Emerald
T2	FLASH BOUNTY	Purple
T3	COMMUNITY PICKS	Cyan
T4	HOT BOUNTY	Gold
T5	LAST CALL	Magenta

Key Features

• ✅ Dark theme matching SolFoundry brand (bg: #0d0d0f, emerald: #10b981, magenta: #ec4899)
• ✅ Editable text zones for bounty title, reward amount, description
• ✅ Tier badges (T1/T2/T3) color-coded
• ✅ SVG source files — open in Figma, Canva, Inkscape, Illustrator
• ✅ PNG preview renders (directly usable)
• ✅ Python generator script () — regenerate with custom text in one command

Design System

• Fonts: Inter (or Arial fallback)
• Colors: Background #0d0d0f, Surface #1a1a1f, Emerald #10b981, Magenta #ec4899
• Gradient: Emerald (#10b981) → Cyan (#06b6d4) accent bars
• Corner radius: 16px cards, 8px inner elements

Files Changed

Acceptance Criteria

• 5 templates delivered in PNG + SVG source format
• Match SolFoundry brand guidelines
• Editable for future bounty announcements

Testing

• All SVG files validated: valid XML, proper gradient definitions, all text elements render
• All PNG files generated: 1080×1080 (40KB) and 1200×675 (30KB)

Closes #829