fix(frameworks): re-assert SSR public invoker on deploy

[leoortizz]

Description

Fixes #10631.

Framework SSR runs on a Cloud Run function that Hosting invokes anonymously, so its service needs allUsers as run.invoker. The generated function declares no invoker, so only the create path set it and the update path never re-applied it. When that binding gets removed out-of-band such as by an org policy, later deploys don't restore it, and hosting:channel:deploy ships a channel that 403s on all server-rendered content while reporting success.

This adds run.ensureInvokerPublic(service), called for frameworks SSR functions on deploy. It is additive: it appends allUsers, keeps any existing invoker members, and is a no-op when allUsers is already present, so it never overwrites deliberate IAM changes. It is also non-fatal: if the grant is blocked it logs a warning instead of failing the deploy. The check is scoped to frameworks codebases, so other functions are untouched.

Scenarios Tested

Ran a Next.js app with next/image and dynamic routes on a live project. I stripped allUsers and ran hosting:channel:deploy; the binding was restored automatically and server-rendered routes returned 200. I then pre-seeded a custom invoker service account, stripped allUsers, and deployed; allUsers was added back and the custom account was preserved.

The issue author suspected the preview deploys might be stripping the binding, so I checked: shipped 15.19.1 does not modify the invoker policy on live or channel deploys, which points to the loss being external rather than deploy-caused.

Added unit tests for ensureInvokerPublic covering add, additive, and no-op, and for the updateV2Function branch covering ensure, warn-on-failure, and skip for non-frameworks functions.

Sample Commands

No new commands or flags.

firebase deploy --only hosting
firebase hosting:channel:deploy preview

[gemini-code-assist]

Code Review

This pull request introduces changes to ensure that frameworks-managed SSR functions remain publicly invokable by additively granting the allUsers member the Cloud Run Invoker role (roles/run.invoker). This is implemented via a new ensureInvokerPublic utility in src/gcp/run.ts and integrated into the Fabricator deployment flow. Feedback on the changes highlights a potential TypeError in src/gcp/run.ts if currentInvokerBinding.members is undefined, suggesting the use of optional chaining to safely check for the presence of allUsers.