Replace "Explore" Tab with "My Clips" Tab

[Emmzyemms]

Labels: good first issue navigation beginner

Description:
The bottom tab bar currently shows "Home" and "Explore". According to the design, the tabs should be "Home", "Upload", "My Clips", and "Profile". The "Explore" tab and screen should be renamed/replaced to match the intended navigation structure.

Acceptance Criteria:

• Tab bar shows: Home, Upload, My Clips, Profile
• Each tab navigates to its corresponding screen (screens can be placeholder views for now)
• Active tab icon and label turns teal (#00E5A0 or theme accent)
• Tab icons are updated to match the design (house, upload cloud, film strip, person)
• Old explore.tsx is removed or repurposed

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