build(deps): bump golang.org/x/crypto from 0.33.0 to 0.52.0

[dependabot]

Bumps golang.org/x/crypto from 0.33.0 to 0.52.0.

Commits

• a1c0d99 go.mod: update golang.org/x dependencies
• 3c7c869 ssh: fix deadlock on unexpected channel responses
• 533fb3f ssh: fix source-address critical option bypass
• abbc44d ssh: fix incorrect operator order
• e052873 ssh: fix infinite loop on large channel writes due to integer overflow
• b61cf85 ssh: enforce user presence verification for security keys
• 9c2cd33 ssh: enforce strict limits on DSA key parameters
• 8907318 ssh: reject RSA keys with excessively large moduli
• ffd87b4 ssh: fix panic when authority callbacks are nil
• 4e7a738 ssh: fix deadlock on unexpected global responses
• Additional commits viewable in compare view

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[talmacschen-arch]

LGTM — approving.

Verified locally by checking out the PR head (base = current main @ 6341803, already on go 1.25) in an isolated worktree:

• go mod verify — all modules verified
• go build ./... — passes
• go vet ./... — clean (see note below)
• make unit — all 5 suites pass (dbconn 12/12, backup 469/470 + skips, TOC 45/45, testutils 8/8, utils 58/58)
• go mod tidy — no diff; go.mod/go.sum are consistent

Risk is minimal: golang.org/x/crypto is an // indirect dependency and go mod why reports main module does not need package golang.org/x/crypto, so no source path in cbcopy exercises it. This is dependency hygiene (clears the Dependabot security alert). The bump also pulls the required updates to the transitive x/net, x/sys, x/text, and x/tools, which is expected.

Note (pre-existing, not introduced by this PR): go vet reports testutils/functions.go:648:2: unreachable code. A go.mod version bump can't introduce that; it lives in test code on main and can be cleaned up separately.

[talmacschen-arch]

Note: the pre-existing go vet warning I mentioned above (testutils/functions.go:648:2: unreachable code) is now tracked separately in #48. It is unrelated to this dependency bump and does not block merging this PR.