last used pair across all pages

[zavelevsky]

fixes #1331

When visiting the following pages: trade, explore (by pair), simulate, create strategy - the selected pair becomes the default pair.

Note - the current behavior is buggy.
If you start to create a strategy and select a pair that doesn't exist yet it becomes the default pair, even if you don't complete the strategy creation - ending up with a bad "empty" experience in other pages.
It can also be more problematic with imported tokens etc.

I personally think that strategy creation shouldn't dictate the pair - or it should only take place once the strategy was created - or only if the pair already exists.

[cloudflare-workers-and-pages]

Deploying carbon-app-sei with    Cloudflare Pages

Latest commit:	68b7768
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Branch Preview URL:	https://feature-default-pair-1331.carbon-app-sei.pages.dev

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[ashachaf]

• explore page cannot handle tokens with no pair
  flow:

1. go to create strategy
2. import this token 0x809FF4801aA5bDb33045d1fEC810D082490D63a4
3. go to trade -> it identify there is no data for the token pair and indicate "no data"
4. go to explore
   expected: identify there is no data for the token pair and indicate "no data" as we do for a pair with no strategies (here)
   actual: there is no token indication in the search url and the page is stuck on endless loading.

[cloudflare-workers-and-pages]

Deploying carbon-app with    Cloudflare Pages

Latest commit:	43c297b
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[tiagofilipenunes]

Just two suggested changes for when the pair doesn't exist in the simulate and explore tab. The addresses may be present in the search but they can be invalid, in which case let's not set the tradePair