Per-App Mock and Debug Runtime Modes for `styfi`, `veyfi`, and `yeth` (backward-compatible)

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Description
Today, mock behavior is mostly controlled globally via NEXT_PUBLIC_USE_MOCKS and NEXT_PUBLIC_E2E, while yeth is separately hardcoded to mock. This works for current preprod usage, but it does not support granular per-app runtime control (styfi on-chain, veyfi on-chain, yeth mock/debug) in a first-class way.

Implement per-app runtime mode resolution with minimal complexity and full backward compatibility.

• Add new envs:

• NEXT_PUBLIC_MOCK_APPS as CSV with allowed values styfi,veyfi,yeth, plus all and none.

• NEXT_PUBLIC_DEBUG_APPS as CSV with same allowed values; default to NEXT_PUBLIC_MOCK_APPS when unset.

• Keep NEXT_PUBLIC_E2E global in this phase.

• Add a single runtime resolver module that returns:

• mockByApp: { styfi: boolean, veyfi: boolean, yeth: boolean }

• debugByApp: { styfi: boolean, veyfi: boolean, yeth: boolean }

• Legacy fallback behavior when NEXT_PUBLIC_MOCK_APPS is unset:

• NEXT_PUBLIC_USE_MOCKS=true -> all apps mock.

• NEXT_PUBLIC_USE_MOCKS=false -> yeth mock, styfi/veyfi on-chain (current behavior).

• Update protocol wiring and consumers to use app-specific mode flags instead of one shared usesMockBackend boolean for all apps.

• Update debug controls rendering to use per-app debug flags.

• Keep production safety checks strict:

• In production runtime, styfi/veyfi mock mode must be forbidden.

• yeth production gating should remain aligned with existing NEXT_PUBLIC_ENABLE_YETH behavior.

• Update tests and docs to cover the new mode matrix and backward compatibility.

• Remove obvious redundancy while touching this area (for example, unused protocol flags), but avoid unrelated refactors.

Acceptance Criteria

• Can run styfi and veyfi on-chain while yeth remains mock in the same deployment.
• Can independently enable/disable app debug controls without changing app backend mode.
• Existing setups that only use NEXT_PUBLIC_USE_MOCKS continue to behave exactly as today.
• Production invariant checks fail when styfi or veyfi mock mode is enabled in production runtime.
• Unit tests cover env parsing and resolved app mode combinations.
• Existing e2e flows continue passing under current CI env defaults.

Out of Scope

• Per-app E2E connector behavior.
• Any yETH on-chain client integration work.
• Broad architectural cleanup outside runtime mode wiring.