Build multilingual web + iOS + Android price-comparison platform

We are building a multilingual price comparison and on-platform switching platform for utilities in Spain. The MVP is already live as a web demo. We are now scoping the full build. This is a real commercial product — not an exploration or proof of concept. We are looking for a long-term development partner (agency or senior team) to deliver the full launch version and continue with us on follow-up work after launch. What the full launch version needs to include: Web app + iOS app + Android app Price comparison across three categories: electricity, gas, and fuel (petrol stations) Full on-platform switching: the user picks a provider, fills in their details inside our platform, and we send a complete contract request to the provider via their API. No call-center handoff. 2 to 3 energy provider API integrations at launch (partnerships already in negotiation) 30+ languages with AI-first translation Comprehensive admin panel so I can manage providers, tariffs, content, translations, and view basic analytics myself as a non-technical founder User accounts: sign up, log in, personal dashboard Bill upload feature: user takes a photo of their current bill and the platform auto-fills their personal data Switch status tracking: after the user submits a switch, they see the status (pending / confirmed / rejected) inside the platform Spain only at launch Tech stack: Not locked in. I want your honest recommendation based on what fits this scope, budget, and timeline. You will not inherit decisions made before you joined. Legal / compliance scope: You are not responsible for legal advice. I will engage a specialised Spanish data protection / GDPR lawyer separately to handle the legal side (privacy policy, cookie banner text, AEPD compliance, etc.). Your job is to build the technical implementation to whatever requirements I provide you from that lawyer. Timeline: 3 to 5 months from signing the contract to launch. Working language: English is required for all communication. Russian-speaking is a strong plus — it makes detailed technical conversations easier for me — but not a hard requirement. Team location: EU-based teams only. I have a strong preference for Eastern European EU countries (Poland, Romania, Bulgaria, Czech Republic, Lithuania, Estonia, Latvia, Hungary, Slovakia, Slovenia). No teams from outside the EU. Who I will sign with (this is non-negotiable): I will only contract with a registered company — a real legal entity with proper business registration in its jurisdiction. Not an individual freelancer, not a shell, not a "we'll figure out the paperwork later" arrangement. I am signing a binding services agreement directly with the company you operate. The contract must clearly cover: Full IP ownership. All code, designs, assets, documentation, and deliverables produced under the engagement are mine, work-for-hire, transferred to me on creation and not on final payment. The repository is in my GitHub organization from the first commit. Milestone-based payments with specific deliverables tied to each milestone. No upfront lump sum. Payments released on milestone acceptance. A defined delivery timeline with named milestones and target dates. A warranty period after launch for fixing defects at no additional cost. Dispute resolution and governing law specified upfront in an EU jurisdiction. Clear scope freeze and change-request process so we both agree what's in and what's out. In your proposal, please describe your standard contract structure for these points. If you cannot meet any of these terms, say so up front. What I want from you in your proposal: Two or three reference projects of similar scope with public URLs (must include at least one combined web + mobile build with third-party API integrations) Your proposed tech stack with a one-paragraph justification per choice Realistic timeline by phase Named team members (LinkedIn + one-paragraph bio per person who would actually work on this — no anonymous teams) Fixed-price proposal with a milestone breakdown Your standard contract terms covering everything in the section above Two client references willing to take a 15-minute call Confidentiality: The full product name, the live MVP link, provider partner names, my budget, and other strategic details are shared only with shortlisted candidates after we sign a mutual NDA. We use Upwork's NDA workflow. How I evaluate: Not lowest bid. I evaluate in this order: reference projects matching this scope, named team quality, contract clarity, tech stack justification, communication quality. Generic agency pitches that don't reference my scope are filtered out automatically. If you've built a comparable multilingual web + mobile platform with third-party API integrations and can show it publicly, please lead with that reference.