feat(mobile): Memories activity is now full screen, better image fit, adds progress indicator

[martyfuhry]

• Similar to the full-screen activity view of the gallery page, this will hide the system navigation bars when you enter the memories activity.
• The navigation bars will return when you leave the activity.
• Adds a progress bar at the top which animates along with the page moving
• Computes aspect ratio of the photo and the available space; if the aspect ratios are nearly identical, then use much better looking BoxFit.cover image fit
• Removes the "1|12" text in the top right
• Refactors the widget to use more page controllers
• Changed the close icon to have a little more contrast
• Close icon now stays in the same place during page transitions

[cloudflare-pages]

Deploying with    Cloudflare Pages

Latest commit:	1ae303a
Status:	⚡️  Build in progress...

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[martyfuhry]

Ah, shoot I gotta dispose those PageController objects. But this is a HookConsumerWidget so I don't have a dispose method. Hold on while I fix that.

[martyfuhry]

OK, I'm back to using Flutter Hooks once more. This is working fine and ready for review!

[martyfuhry]

The latest commit adds ticks to the progress bar:

I'd love to get some kind of autoplay working, but it's proven a bit more challenging than I'd like for this PR. So I'll open a new one for that later.

[martyfuhry]

With rounded edges: