Improve interactive calendar with visual posting aids

Update calendar component with custom DateTimePicker, visual indicators for occupied dates and optimal posting times, and French locale support.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: ae4037a0-2a6f-4530-9bac-79b543286bda
Replit-Commit-Checkpoint-Type: intermediate_checkpoint
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/397bca8c-984f-43ff-841a-10897aeb8140/ae4037a0-2a6f-4530-9bac-79b543286bda/aGnsIb5

replit.md

@@ -11,7 +11,7 @@ Preferred communication style: Simple, everyday language.
 ## Recent Changes
 
 ### October 28, 2025
-- **Calendar Mobile UX Improvements**: Enhanced mobile calendar and publication planning interface with three visual improvements: (1) Mobile calendar list now displays today's date at the top, before chronological ordering, for quick access to current day's publications; (2) Added green visual indicators in new-post page showing optimal posting times (8h-9h, 12h-14h, 18h-21h) to maximize audience reach; (3) Added red visual indicators showing dates with existing scheduled posts to prevent scheduling conflicts. Both indicators appear dynamically below the datetime selector, displaying up to 5 dates with option to view more.
+- **Interactive Calendar with Visual Indicators**: Replaced native datetime-local input with custom DateTimePicker component featuring visual planning aids. Calendar displays occupied dates with red background (bg-red-500/20) to prevent scheduling conflicts. Time selector highlights optimal posting hours (8h, 12h-13h, 18h-20h) with green background (bg-green-500/20) and sparkle emoji to maximize audience engagement. Component includes clear button (X icon) to quickly return to immediate publishing, useEffect synchronization for external state updates, and French locale support via date-fns. Mobile calendar list still displays today's date first for quick access.
 - **Facebook Video Story Publishing Fix**: Fixed critical bug preventing video story publication. Facebook Graph API requires a 3-phase upload process for video stories: (1) START phase - initialize upload session and get `video_id` + `upload_url`, (2) UPLOAD phase - POST video to rupload.facebook.com endpoint with `file_url` header and OAuth authorization, (3) FINISH phase - finalize and publish story with `video_id`. Previous implementation incorrectly attempted direct upload to `/video_stories` endpoint with `file_url` parameter, causing "#100 The parameter upload_phase is required" error. Fixed by implementing proper 3-phase workflow using remote URL upload method (file_url header), avoiding need for binary chunked uploads.
 
 ### October 17, 2025