Add Gemini 3.5 model-selection idea to backlog

Triaged from the cross-project inbox. Needs a research pass to confirm
available stable Gemini versions before wiring; flag the server+client
model-list duplication and the matching relay-side capture.

ROADMAP.md

@@ -11,6 +11,7 @@ Longer-term backlog for Recaps. Near-term in-flight work and known issues live i
 - **Zaprite recurring card billing (BLOCKED on Zaprite).** Grant wants card payments to DEFAULT to recurring (buyer can opt out at checkout). Zaprite's public API (`api.zaprite.com/openapi.json`) only creates one-time `/v1/orders` — recurring is a hosted/dashboard feature with no per-buyer metadata, no renewal webhook, and no billing-portal URL via API. The shipped card rail is one-time prepaid. UNBLOCK by confirming with Zaprite support whether the account can: (a) attach a per-buyer reference/metadata to a recurring checkout (so a payment maps to a Recaps user), (b) fire a webhook on each renewal charge (so we extend the tier each period), (c) expose a customer/billing-portal URL (for the chosen "link to Zaprite portal" cancel path). Decisions already made: no reminder emails for auto-renewing cards; a failed charge = lapse at period end (the relay's expiry-enforcement already does this — a missed renewal just doesn't extend `expires_at`).
 - **Close the architecture-simplification gaps** (`docs/architecture-simplification-plan.md`). After core-decoupling + self-serve, these steps remain OPEN: **(8) "Take Recaps home"** — mint a fresh Keysat token on demand at click time; likely BROKEN today because relay-tier cloud users have no `keysat_license` for `/api/account/license-key` to return. **(10) cloud paid-only** — the free signed-in tier + signup-grant credits are still live; the plan wanted cloud to be paid-only with self-hosted as the free path (product call — confirm intent before building). **(5, partial) anon signup→Pro** still routes through `/api/license/purchase` + `pending_signups` (Keysat license) instead of the relay tier like the signed-in flow does. **(6, partial) tokenized renew** — the reminder email's renew link is `?renew=1` (requires sign-in); the plan wanted a one-time-token `/renew?token=…` for friction-free renewal. NOTE: the doc's Zaprite-*recurring* / cancel-button / Recaps-DB-owns-expiry parts were intentionally SUPERSEDED by the prepaid + relay-owns-tier model — don't build those.
 - **Decide the Max tier-quota default.** The relay code default is `max.monthly: null` (unlimited) → cards render "Unlimited" on a fresh install. The operator set `max.monthly: 120` on their box via the Adjust-Tier-Quotas action (so cards show 120 there). Decide whether a metered number (e.g. 120) should be the shipped default in `recap-relay/server/config.js` — note it also enforces the ceiling, not just the card label.
+- **Add Gemini 3.5 to model selection.** First have a research agent confirm which stable Gemini model versions are actually available and the correct model id/name before wiring anything. The model list is duplicated server + client (provider config under `server/providers/` + the model picker in `public/index.html`) — add the option in lockstep, like the URL-parser convention. Coordinate with the matching relay-side capture (the relay routes Gemini, so its model list must agree). — captured 2026-06-16
 
 ## Known debt (P2, from the 2026-06-14 full-eval — `EVALUATION.md`)