fix(api): authorize API-key clients on delete/cancel purchase permission check

[cristim]

Summary

requireDeleteOrCancelPurchasePermission (gating DELETE /api/purchases/planned/{id}) hand-rolled its own auth dispatch instead of using the shared requirePermission path, and in doing so dropped the user-API-key branch entirely. A scoped API-key automation client presenting only an x-api-key header (no bearer token) got a 401 no authorization token provided on delete/cancel, even when the key held delete:purchases.

This is a follow-up to #1421, which introduced the hand-rolled gate while adding cancel-own support.

Fix

• Added requireAnyPermission / authorizeAPIKeyAny as multi-verb counterparts to the existing requirePermission / authorizeAPIKey dispatch chain (principal-in-context -> admin API key -> user API key -> bearer-token session), so a multi-verb gate can't drift from the single-verb dispatch order every other endpoint relies on.
• requireDeleteOrCancelPurchasePermission now delegates to requireAnyPermission instead of hand-rolling dispatch.
• Widened the verb set to include update-any so a custom group holding only that permission clears this entry gate before the ownership check runs (documented in the code comment; doesn't widen the effective grant since update-any already passes the later ownership-scoped cancel check).
• Both authorizeAPIKey and authorizeAPIKeyAny fail closed: an incomplete identity after a granted check is a hard error, and a denied-but-valid key returns 403 rather than silently falling through to bearer-token auth.

Test plan

• go build ./... — clean
• go vet ./... — clean
• go test ./... (full repo) — all packages pass, 0 failures
• Regression test TestHandler_deletePlannedPurchase_UserAPIKey_Allowed verified to fail pre-fix (401 no authorization token provided, reproducing the reported bug) and pass post-fix
• Updated pre-existing sibling test TestDeletePlannedPurchase_PermissionGate whose mock set predated the update-any verb addition
• golangci-lint (CI-pinned v2.10.1) on internal/api/...: 2 pre-existing findings, both outside this diff's changed lines (unrelated debt at handler_purchases.go:1832 and :2545)
• gocyclo -over 10 on changed files: clean

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Review details

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 73136e61-84d8-4bf7-851e-69d6443cc662

📥 Commits

Reviewing files that changed from the base of the PR and between f8cdea6 and 3766119.

⛔ Files ignored due to path filters (1)

• go.work.sum is excluded by !**/*.sum

📒 Files selected for processing (4)

• internal/api/handler.go
• internal/api/handler_purchases.go
• internal/api/handler_purchases_test.go
• internal/api/router_660_permission_flips_test.go

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/1421-apikey-delete-cancel-auth

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[cristim]

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