Add Telegram alerts bot link to monitoring frontend footer

[TaprootFreak]

Summary

The monitoring frontend (mainnet + testnet, both PRD and DEV) had no footer or social links. Adds a minimal footer with a "Get alerts" Telegram CTA pointing to the env+chain-correct bot.

• Bot URLs (4 in total: mainnet|testnet × prd|dev) live as code config in frontend/src/constants.ts — no env variable carries the URL string itself.
• DEV vs PRD is baked into each image at build time via Docker build-args, with strict VITE_DEPLOYMENT_ENV validation in constants.ts (throws on missing/invalid value, no fallback).
• Chain is resolved at runtime from window.location.hostname (testnet domains → testnet, else mainnet) — the same image is reused for both monitoring.juicedollar.com and monitoring.testnet.juicedollar.com.
• Single right-aligned anchor with inline Telegram SVG icon, aria-label="Telegram alerts bot". Footer sticks to the bottom via flex flex-col on the app shell.

Bot mapping (per issue DFXswiss/server#103)

Deployment	Hostname	Bot
PRD mainnet	monitoring.juicedollar.com	@juicedollar_monitor_prd_bot
DEV mainnet	dev.monitoring.juicedollar.com	@juicedollar_monitor_dev_bot
PRD testnet	monitoring.testnet.juicedollar.com	@juicedollar_monitor_tst_prd_bot
DEV testnet	dev.monitoring.testnet.juicedollar.com	@juicedollar_monitor_tst_dev_bot

Pipeline

Stage	File	Mechanism
Image build (DEV, both build and deploy jobs)	.github/workflows/frontend-dev.yaml	--build-arg VITE_DEPLOYMENT_ENV=dev
Image build (PRD, both build and deploy jobs)	.github/workflows/frontend-prd.yaml	--build-arg VITE_DEPLOYMENT_ENV=prd
frontend/Dockerfile	ARG/ENV pair before npm run build
Runtime	nginx static, no compose change	:beta and :latest images each carry their fixed VITE_DEPLOYMENT_ENV; chain resolved client-side from hostname

Test plan

• VITE_DEPLOYMENT_ENV=prd npm run build succeeds; bundle contains all 4 bot URLs (chain lookup is runtime).
• VITE_DEPLOYMENT_ENV=dev npm run build succeeds.
• npm run build without env still bundles (Vite does not execute top-level throw at build); validation throws at page-load — fail-loud at first browser hit, no silent fallback.
• DEV CI workflow builds :beta image → dev.monitoring.juicedollar.com shows @juicedollar_monitor_dev_bot, dev.monitoring.testnet.juicedollar.com shows @juicedollar_monitor_tst_dev_bot.
• PRD CI workflow builds :latest image → monitoring.juicedollar.com shows @juicedollar_monitor_prd_bot, monitoring.testnet.juicedollar.com shows @juicedollar_monitor_tst_prd_bot.

Notes

• This mirrors d-EURO/monitoring#62 (already merged) — same Vite/build-args pattern, plus a chain dimension (window.location.hostname check) because JuiceDollar runs the same image on both Citrea Mainnet and Testnet.
• No DFXswiss/server compose change is required for this PR. The image is environment-baked; chain selection follows from the hostname.
• npm run lint reports 3 pre-existing errors unrelated to this PR (PositionsTable.tsx, Table.tsx, api.hook.ts); not addressed here.