[CORE-363] Upgrade GitHub Actions Dependencies and Refresh Generated Mocks

[dytsou]

Type of changes

• Chore

Purpose

• Bring CI workflow action and tool pins up to current majors so builds stay on supported runners and patched toolchains.
• Align sqlc across Test and Build jobs and regenerate mockery mocks so generated helpers match current interface signatures.

Additional Information

• Updated workflows: pre-commit.yaml, release.yaml, snapshot.yaml
  • actions/checkout v4 → v7, actions/setup-go v5 → v6, actions/github-script v7 → v9
  • Docker actions: buildx/login v3 → v4, build-push-action v6 → v7
  • sqlc 1.25.0/1.28.0 → 1.31.1, mockery 3.5.5 → 3.7.1, golangci-lint v2.12 → v2.12.2
• Regenerated: internal/form/workflow/mocks/{Querier,Validator}.go, internal/inbox/mocks/Store.go

Side effect analysis

Upgrade	Possible break	Our usage
checkout v4→v7	Node 24; v7 blocks fork checkout for pull_request_target / workflow_run	Uses pull_request / push + ubuntu-latest → no impact
setup-go v5→v6	Toolchain resolution, Node 24	Pinned go-version: "1.26.2" (matches go.mod) → no impact
github-script v7→v9	Cannot require('@actions/github')	Only uses github.rest.pulls.list → no impact
Docker buildx/login/build-push majors	Removed old inputs/envs (install, config, DOCKER_BUILD_NO_SUMMARY, etc.)	Not used → no impact
sqlc → 1.31.1	Generated type changes	Local sqlc generate with 1.31.1: 0 diff; already on pgx/v5 → no impact (Build pin alignment also removes 1.25.0 inconsistency)
mockery → 3.7.1	Regenerated output may change	Mocks regenerated in this PR to match current interfaces → CI-safe
golangci-lint → v2.12.2	Patch bump	Low risk