feat: persistence and reconnect flow

[bernardev254]

summary

Implements Freighter persistence and reconnect flow.

changes:

• Restores allowed Freighter sessions on reload via isConnected() + isAllowed().
• Persists active Stellar network and updates signing, RPC, Horizon, labels, and explorer links.
• Watches Freighter account/network changes using WatchWalletChanges.
• Re-derives Stellar stealth keys on network switch without another signature prompt.
• Clears keys safely on disconnect or account switch.
• Syncs session updates and disconnects across tabs with BroadcastChannel.
• Adds friendly Install Freighter and Approve in Freighter CTAs, with 2-second install polling for 30 seconds.
  closes Freighter session persistence + auto-reconnect #4

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[truthixify]

Closing as duplicate. Issue #4 is being handled in #38 which was opened first (currently waiting on a rebase).

If #38 doesn't include the AutoSign behavior on reconnect that's in this PR, that could be a quick follow-up PR once #38 lands. Worth flagging on issue #4 so the eventual final state captures both threads.

Other open Stellar Wave issues: https://github.com/wraith-protocol/demo/issues?q=is%3Aopen+label%3A%22Stellar+Wave%22

Thanks @bernardev254.