feat(APP-1054): Implement gasLimit param (8/10)

[milosh86]

Description

Closes APP-1054.

Replaces the hardcoded 1_000_000 placeholder _gasLimit (left as a TODO(APP-1029) in the forward-message action)
with a real, required gas-limit field backed by a backend simulation.

• Backend simulation — crossChainControllerService.estimateGasLimit (new
  POST /v2/simulations/:network/cross-chain/:controllerAddress/gas-limit) simulates the inbound delivery on the
  destination chain and returns the measured requiredGas, since eth_estimateGas can't measure it: the controller
  wraps the payload in a try/catch, so the node's binary search only ever prices the catch branch.
• Client-side policy — crossChainControllerGasUtils.resolveGasLimit turns the raw measurement into a submittable
  limit by applying a 30% safety margin (justified in crossChainControllerGas — the payload is arbitrary
  user-composed actions, frozen into calldata weeks before execution, five call-frames deep), a 200k floor (the CCIP
  default), and a 3M cap (the lane's typical maxPerMsgGasLimit, since the backend deliberately never checks it).
• GasLimitInput — new number input with a "Calculate" action alongside the usual +/- steppers.
• CrossChainControllerForwardMessageAction — the gas-limit field is required (an unset limit risks the message
  landing "delivered but not executed", recoverable only via a permissioned retry on the destination chain) and is
  cleared whenever the destination chain or the action list changes, since a limit measured for a different payload is
  worse than none. Surfaces the simulation outcome (success/reverted/margin-reduced/exceeds-cap) as an inline alert,
  with a link to the saved Tenderly simulation when available.

Dependencies: stacked on app-1056-show-warning-about-controller-fee-balance → app-1053-… → main. Merge the
bases first.

Type of Change

• Minor: Feature (non-breaking change which adds new functionality)

Developer Checklist:

• Manually smoke tested the functionality in a preview or locally
• Confirmed there are no new warnings or errors in the browser console
• (For User Stories only) Double-checked that all Acceptance Criteria are satisfied
• Confirmed there are no new warnings on automated tests
• Merged and published any dependent changes in downstream modules
• Selected the correct base branch
• Commented the code in hard-to-understand areas
• Followed the code style guidelines of this project
• Reviewed that the Files Changed in Github's UI reflect my intended changes
• Confirmed the pipeline checks are not failing

Review Checklist:

• (For User Stories only) Tested in a preview or locally that all Acceptance Criteria are satisfied
• Confirmed that changes follow the code style guidelines of this project

[linear-code]

APP-1054

[github-actions]

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[github-actions]

E2E results (preview)

Smoke

Base URL	https://app-next-m5y09of9o-aragon-app.vercel.app
Suite	smoke
Playwright result	✅ passed
Summary	82 passed
HTML report	View report
GitHub job	✅ completed

View run #4915