Slice 1: scaffolding + propose-to-super-draft vertical

Brings the §1 bot wrapper, the §4 cache (webhook + reconciler), the
§5 schema (six numbered migrations), Gitea OAuth + §6 user
provisioning, the §7 catalog left pane, and the propose-to-merge
vertical: propose modal opens an idea PR against the meta repo, an
owner merges from the pending-idea view, the cache picks it up via
webhook or reconciler sweep, and the catalog renders the new
super-draft.

Per §1 the bot is the only Git writer; every commit, branch
creation, and PR merge carries the §6.5 On-behalf-of: trailer and
an `actions` audit row. Per §4 the cache is never written from a
user action — it's webhook+reconciler only.

Covered by `backend/tests/test_propose_vertical.py` against an
in-process Gitea simulator.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/.env.example

@@ -0,0 +1,43 @@
+# --- Gitea ---
+# Base URL of the Gitea instance the app speaks to.
+GITEA_URL=http://localhost:3000
+
+# The bot service account that performs every Git operation per §1.
+# Provision a real Gitea user, generate a personal access token with
+# repo and admin (or at minimum: repo, write:repository) scopes, and
+# put the token here. The bot is the only Git writer.
+GITEA_BOT_USER=rfc-bot
+GITEA_BOT_TOKEN=
+
+# The Gitea org or user that owns the meta repo and every RFC repo
+# the bot will create on graduation.
+GITEA_ORG=wiggleverse
+META_REPO=meta
+
+# --- OAuth (Gitea) ---
+# In Gitea: Site Administration → Applications → Add OAuth2 Application.
+# Redirect URI: {APP_URL}/auth/callback
+OAUTH_CLIENT_ID=
+OAUTH_CLIENT_SECRET=
+
+# --- App ---
+APP_URL=http://localhost:8000
+SECRET_KEY=change-me-to-a-long-random-string
+DATABASE_PATH=data/rfc-app.db
+
+# Per §1: owner zero. The Gitea login that gets the owner role on
+# first sign-in.
+OWNER_GITEA_LOGIN=ben
+
+# Webhook signature secret. Gitea sends X-Gitea-Signature as the
+# HMAC-SHA256 of the body using this secret. Per §4.1 the webhook is
+# one of two cache writers; signing keeps spurious writes out.
+GITEA_WEBHOOK_SECRET=change-me-to-a-shared-secret
+
+# --- LLM providers (carryover §18) ---
+# Comma-separated list of provider keys to enable. Per the §19.2
+# per-RFC-model topic, this is app-wide until that topic lands.
+ENABLED_MODELS=claude
+ANTHROPIC_API_KEY=
+GOOGLE_API_KEY=
+OPENAI_API_KEY=