[emperorsominian-droid]

Closes #1765
Closes #1766
Closes #1767
Closes #1768

• Bet amount validation allows exponent notation, more than 7 decimals and values below the contract minimum #1765: strict decimal regex (max 7 decimals), BigInt stroop conversion, minimum-bet constant
• SUPPORTED_ASSETS hard-codes one network's issuer/contract addresses while the app defaults to TESTNET #1766: asset registry keyed by NEXT_PUBLIC_STELLAR_NETWORK with address validation; PIQ via NEXT_PUBLIC_PIQ_TOKEN_ADDRESS
• Dispute page declares params as a plain object, but App Router passes a Promise #1767: dispute page reads params with use(params)
• Create-market page ignores the API error body and shows only 'Failed to create market (status)' #1768: create-market parses API error body into ApiError and maps via describeWriteError

Tests: new regression tests for amount parsing and asset registry; PlaceBetForm tests pass.