Route GeckoTerminal via pricing-proxy

[TaprootFreak]

Summary

Adds the required `GECKOTERMINAL_BASE_URL` env var to point the GeckoTerminal upstream at the in-cluster pricing-proxy (DFXswiss/pricing-proxy) instead of `api.geckoterminal.com` directly. Mirrors the `COINGECKO_BASE_URL` plumbing from #31 — same construction-time hard-fail, same .env wording, same getter shape.

Why

GeckoTerminal's free tier shares a single 30 req/min IP quota across every consumer on the host. Three monitoring stacks (d-EURO, JuiceDollar testnet, JuiceDollar mainnet) plus restart-bursts already produce visible 429s on dfxdev:

```
deuro-deuro-monitoring-1 | ERROR [PriceService] AxiosError: Request failed with status code 429
deuro-deuro-monitoring-1 | WARN [PriceService] Returning expired cached prices due to API error
```

The pricing-proxy now exposes a `/geckoterminal/` route (pricing-proxy#3) with the same 60 s shared cache, request coalescing and validation pipeline already in front of CoinGecko Pro. Pointing this service at it collapses the three independent streams into one upstream call per 60 s.

What changes

• `src/config/monitoring.config.ts` — new `geckoTerminalBaseUrl?: string` field plumbed from `GECKOTERMINAL_BASE_URL`.
• `src/config/config.service.ts` — getter, same shape as `coingeckoBaseUrl`.
• `src/monitoringV2/price.service.ts` —
  • Constructor hard-fails when `GECKOTERMINAL_BASE_URL` is unset, same as for `COINGECKO_BASE_URL`. No silent anonymous fallback.
  • Misnomer fix: `getCoinGeckoPricesInUSD` → `getGeckoTerminalPricesInUSD` (and the local `coinGeckoPrices` variable in `getTokenPricesInEur`). The function has always called `api.geckoterminal.com`, not CoinGecko — the name was a relic from before the GT path was split out. Matches the helper name already in use in the downstream fork at `JuiceDollar/monitoring`.
• `.env.example` — documents the new var as required, parallel to `COINGECKO_BASE_URL`.

Breaking — rollout order matters

`GECKOTERMINAL_BASE_URL` is required. A container started without it now refuses to construct and the deploy will roll back. The server-side compose update on `DFXswiss/server` (adding the env to `deuro-monitoring` on dfxdev + dfxprd) must therefore be in place before the Auto-Release-PR for this repo lands on `main` and the `:latest` image rebuilds.

Recommended order:

1. Merge this PR → `:beta` rebuilds. dfxdev's `deuro-monitoring` stack will not auto-deploy because the env var isn't set yet; that's fine, the existing container keeps serving.
2. Land the server-repo compose change adding `GECKOTERMINAL_BASE_URL: http://pricing-proxy:8080/geckoterminal\` to `deuro-monitoring` on dfxdev + dfxprd, plus the auto-release PR to `main`. After that deploys, the existing `:latest` container restarts with the env set and keeps working (env is read at startup, old code just ignores the var).
3. Approve the Auto-Release-PR for this repo (develop → main). `:latest` rebuilds. Next `deuro-monitoring` deploy picks up the new image, constructor sees the env, traffic now flows through the proxy.

Test plan

• CI green (build + lint)
• After server-repo compose change lands on dfxdev: existing `deuro-monitoring` container restarts cleanly with `GECKOTERMINAL_BASE_URL` set; logs still show `Fetched prices for N tokens from GeckoTerminal` (old code, still direct path).
• After this PR's auto-release lands on main and the resulting `:latest` deploys: pricing-proxy logs on dfxdev show `/geckoterminal/api/v2/...` traffic from the `deuro-monitoring` container IP, and the 429 lines stop.
• Same verification on dfxprd after the prd-side compose + deploy.