feat(builder): B4 — Akte mode + project-backed scenarios (m/paliad#153)

PRD §2.3 + §10. Implements the dual-write rule (load-bearing
complexity per PRD §10): project-backed scenarios mirror flag
toggles to paliad.projects.scenario_flags and filed event states
to paliad.deadlines, while kontextfrei scenarios continue writing
only to paliad.scenario_events. Visible affordances: page-header
Akte picker, enabled "Aus Akte" mode tab, Akte banner on the
project-backed canvas, cross-surface scenario-flag-changed
dispatch + listener for live peer-surface coherence.

Backend
- ScenarioBuilderService takes ProjectService + ScenarioFlagsService
  deps so dual-write hits live tables.
- CreateScenarioFromProject seeds a scenario from a project: copies
  proceeding_type_id + scenario_flags, normalises our_side to the
  builder's binary claimant|defendant axis, surfaces existing
  rule-bound deadlines as scenario_events (filed when completed,
  planned otherwise).
- PatchProceeding on a project-backed top-level triplet dual-writes
  scenario_flags to projects.scenario_flags via flagDeltaFromBuilder.
- PatchEvent transitioning to state='filed' on a project-backed
  scenario upserts paliad.deadlines (status='completed', completed_
  at, source='rule') inside the same tx as the scenario_events
  UPDATE — canvas and project surfaces never diverge mid-flight.
- POST /api/builder/scenarios/from-project handler wires the entry
  point.

Frontend
- builder-akte.ts: project list fetch + dropdown render, Akte
  banner, createScenarioFromProject POST helper.
- builder.ts: mode branching — picking an Akte (search hit or
  page-header pick) creates a project-backed scenario and loads it;
  loaded scenarios reflect their origin_project_id on the picker +
  banner; flag toggles on Akte-backed top-level triplets dispatch
  scenario-flag-changed so the Verfahrensablauf strip / project
  surfaces refresh; the builder listens to inbound scenario-flag-
  changed and refetches its scenario when the changed project
  matches origin_project_id.
- procedures.tsx: enable the previously-disabled Aus Akte tab.
- i18n + CSS: builder.akte.banner.prefix key (DE+EN); lime-tinted
  banner styling.

Tests
- TestScenarioBuilderAkteDualWrite (live DB) pins the dual-write
  contract: Akte flag toggle → projects.scenario_flags updated,
  Akte filed event → deadlines row inserted; kontextfrei flag
  toggle leaves projects.scenario_flags untouched, kontextfrei
  filed event leaves deadlines untouched.
- Existing TestScenarioBuilderService passes against the new
  signature (nil deps short-circuit dual-write paths).

Verification: go test ./... + go vet ./... + bun run build all
clean. Playwright smoke against the static dist build confirms
the Akte tab + picker render correctly, fetchAkteProjects fires
on mount, and the scenario-flag-changed CustomEvent dispatches +
receives without runtime errors.

t-paliad-347

cmd/server/main.go

@@ -248,8 +248,11 @@ func main() {
 			ScenarioFlags: services.NewScenarioFlagsService(pool, projectSvc),
 			// t-paliad-340 / m/paliad#153 B0 (mig 157) — Litigation Builder.
 			// CRUD over the new normalised scenarios + scenario_proceedings
-			// + scenario_events + scenario_shares tables.
-			ScenarioBuilder: services.NewScenarioBuilderService(pool),
+			// + scenario_events + scenario_shares tables. B4 adds the
+			// Akte-mode dual-write: project-backed scenarios write through
+			// to paliad.projects.scenario_flags + paliad.deadlines via the
+			// injected project + scenarioFlags services.
+			ScenarioBuilder: services.NewScenarioBuilderService(pool, projectSvc, services.NewScenarioFlagsService(pool, projectSvc)),
 		}
 
 		// t-paliad-246 Slice A — Backup Mode runner. Wired only when