Fix sticky board bugs and add responsive mobile navigation

[kiyarose]

Summary

• add a true mobile-only hamburger drawer overlay so navigation feels independent from page content on small screens
• refine sticky controls to emoji/icon actions and prevent accidental text selection while dragging
• allow stickies to be dragged freely beyond the sticky board box into other page areas
• tune weekly projector stat chips/cards (plus streak card sizing) for better mobile scale
• prevent deleted notes and stickies from reappearing by deleting remote records missing from local during sync push

Manual walkthrough artifacts

sticky_free_drag_outside_board_demo.mp4
Sticky dragged beyond board into notepad area
Sticky drag transition outside board
mobile_drawer_and_sticky_icons_demo.mp4
Sticky controls use emoji icons
Mobile hamburger opens as independent drawer
Weekly projector stats resized for mobile

Resolves #7
Resolves #8

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