feat: Sandboxed function execution via FUNCTIONS_DRIVER=docker

Each invoke runs in an ephemeral locked-down container — no network,
read-only rootfs, 128MiB/0.5CPU/64-pid caps, non-root, cap-drop ALL.
Source travels as base64 in the container env and materializes in the
tmpfs, so no bind mount is needed (Docker Desktop / remote daemons work).
Timeout force-removes the named container.

exec driver stays the default; the trust-model docs now describe both.

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Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

CHANGELOG.md

@@ -28,6 +28,7 @@ All notable changes to Primora. Format follows [Keep a Changelog](https://keepac
 - **Presigned object URLs** — `POST /buckets/:bucketID/object-presigns` mints SigV4 query-signed `GET`/`PUT` URLs (60 s–1 h TTL) so clients transfer large objects directly against S3 without proxying through the backend. Read role for downloads (object must exist — no key probing), write role for uploads. `S3_PUBLIC_ENDPOINT` rewrites the client-facing host for internal `S3_ENDPOINT`s; signatures bind the host so URLs are valid only where they were minted. The local driver returns a clear error — a presigned URL needs a real object API.
 - **Desktop auto-updater** — `tauri-plugin-updater` wired end to end: minisign keypair, `createUpdaterArtifacts`, `latest.json` manifest built from signed artifacts on every release, and a silent background check on the connect screen offering "Update & restart" (download → verify → install → relaunch). Unsigned artifacts can never install — missing signature means no manifest, not a bypass. CI signs via `TAURI_SIGNING_PRIVATE_KEY` secrets; OS-level signing (notarization/Authenticode) remains open.
 - **Release SBOMs** — CycloneDX SBOM for each published GHCR image (backend/auth/frontend) plus one for the source tree, attached to every GitHub Release via `anchore/sbom-action`.
+- **Sandboxed function driver** — `FUNCTIONS_DRIVER=docker` runs every invoke in an ephemeral locked-down container: no network, read-only rootfs, 128 MiB memory, 0.5 CPU, 64 pids, non-root, all capabilities dropped. Source is injected via base64 env (no bind mount — works on Docker Desktop and remote daemons); timeout force-removes the container so nothing lingers. Verified live: code runs, network is unreachable inside, and deadline kills land.
 - **Function triggers** (migration 00016) — three new ways to run a function, all through the same executor and run log. Scheduled jobs accept `function_id` instead of `url` (run status mirrors the exit code); inbound hooks gain `mode: "function"` — the received body becomes the function's stdin payload, acked immediately with the run recorded async; and `event_pattern` on a function (`document.*`, `*`, or an exact type) fires it detached whenever a matching domain event publishes — `{event, project_id, occurred_at, data}` as payload. Runs record trigger source: `manual`/`schedule`/`hook`/`event`. Dashboard: function event-trigger field, job target picker (URL or function), and inbound-hook function mode.
 
 ## [0.7.1] - 2026-09-23