fix(security): reject cross-origin requests in TrustedLocal

[aguung]

Summary

• Any web page open in the user's browser could fetch() the local /api and be treated as trusted, because TrustedLocal only checked that the TCP peer was loopback and never checked Origin.
• Adds an Origin-vs-Host check to TrustedLocal, the single choke point already used by Authorized/Require for every /api route.

Problem

• server/middleware/dashboard.go's TrustedLocal grants full /api trust to any loopback-peer request, with no check that it actually originated from enowX's own UI.
• Because no handler restricts Content-Type, a cross-site "simple" request (e.g. Content-Type: text/plain) is delivered by the browser without a CORS preflight even though the attacker page can't read the response — the side effect already happened.
• Concrete impact: server/handlers/api_agent.go's Exec (arbitrary shell command) and FSWrite (arbitrary file write) sit behind this same gate — a single malicious tab open on the user's machine is drive-by RCE. The same hole reaches every other TrustedLocal-gated endpoint (accounts, keys, mitm, integrations, plugins, market).

Solution

• originTrusted(r): if Origin is absent, trust as before (curl, the enx CLI, and local scripts never send an Origin header). If present, it must match the request's own Host — a browser cannot forge Origin, so a mismatch reliably signals a cross-site request even when the TCP peer is genuinely loopback.
• Comparing against r.Host rather than a hardcoded 127.0.0.1/localhost allow-list keeps this correct for every way a user legitimately reaches the app locally (127.0.0.1:PORT, localhost:PORT, [::1]:PORT, or a custom ENOWX_HOST).
• Mirrors the same-origin default already enforced by the WebSocket terminal (server/handlers/api_terminal.go, via nhooyr.io/websocket's default OriginPatterns behavior) — this brings the plain-HTTP /api path to parity with it instead of inventing a new policy.

Changed files

File	Change
server/middleware/dashboard.go	Adds originTrusted; TrustedLocal now also requires it.
server/middleware/dashboard_test.go	New table-driven tests covering no-Origin, matching-Origin, mismatched host/port, null, malformed, and forwarded+matching-Origin cases.

Known limitation

• This compares Origin and Host for consistency, not against a fixed allow-list, so a DNS-rebinding attack (attacker domain resolved to 127.0.0.1) would present a matching-but-attacker-chosen Origin/Host pair and bypass this check. Flagging for visibility; considered out of scope for this fix.

Test plan

• go test ./server/middleware/... -run TestTrustedLocal -v passes (9/9, including 1 pre-existing subtest)
• go build ./... and go test ./... pass with no regressions (41 packages)
• Manually verified against a running instance: a no-Origin request and a matching-Origin request to /api/agent/exec both still execute; a mismatched-Origin request now gets 401 instead of executing