feat: Functions — JS/TS execution with run log

core.functions + core.function_runs: project-scoped code executed by a
runtime binary on the backend host (bun or deno per function). Payload
arrives on stdin + PRIMORA_PAYLOAD env; stdout/stderr captured per run
(capped), with status/exit code/duration. Invoke returns 502 + the
recorded run on failure so errors stay observable.

Dashboard gains a Functions page: code editor, JSON payload invoke,
live result, run history. Runner config via FUNCTIONS_RUNTIME /
FUNCTIONS_TIMEOUT_SECONDS / FUNCTIONS_MAX_OUTPUT_BYTES.

Verified live: bun ran code, stdin payload delivered, error path returns
502 with captured stderr; timeout kills at deadline.

Generated with [Devin](https://devin.ai)

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

apps/backend/internal/database/db/models.go

@@ -266,6 +266,29 @@ type CoreEvent struct {
 	Ts          pgtype.Timestamptz `json:"ts"`
 }
 
+type CoreFunction struct {
+	ID        uuid.UUID          `json:"id"`
+	ProjectID uuid.UUID          `json:"project_id"`
+	Name      string             `json:"name"`
+	Code      string             `json:"code"`
+	Runtime   string             `json:"runtime"`
+	Enabled   bool               `json:"enabled"`
+	CreatedAt pgtype.Timestamptz `json:"created_at"`
+	UpdatedAt pgtype.Timestamptz `json:"updated_at"`
+}
+
+type CoreFunctionRun struct {
+	ID         uuid.UUID          `json:"id"`
+	FunctionID uuid.UUID          `json:"function_id"`
+	Trigger    string             `json:"trigger"`
+	Status     string             `json:"status"`
+	ExitCode   *int32             `json:"exit_code"`
+	Stdout     string             `json:"stdout"`
+	Stderr     string             `json:"stderr"`
+	DurationMs int32              `json:"duration_ms"`
+	CreatedAt  pgtype.Timestamptz `json:"created_at"`
+}
+
 type CoreInboundHook struct {
 	ID             uuid.UUID          `json:"id"`
 	ProjectID      uuid.UUID          `json:"project_id"`