FLW-Mobile-App README improvements - fix numbering, add architecture details and contributing guide

[Jayant-kernel]

Description

The FLW-Mobile-App README has a few gaps that trip up new contributors:

• Duplicate step 7 in the Installation section (one step is missing entirely)
• Typo: statingDebug should be stagingDebug
• Tech stack section only lists MVVM — no mention of Room, Hilt, WorkManager, or how offline sync works
• No link to the Contributor Guidelines anywhere in the repo

Related to #132 (DMP 2026 gamification work).

Changes

• Fixed step numbering in Installation (steps 1–10, no duplicates)
• Fixed stagingDebug typo
• Updated Technologies section with versions and a note on offline-first sync
• Added Contributing section with a link to CONTRIBUTOR_GUIDELINES.md

Acceptance Criteria

• No duplicate step numbers in Installation
• stagingDebug spelled correctly
• Technologies section mentions Room 2.6.1, Hilt, WorkManager 2.10.2, offline-first
• Contributing section links to CONTRIBUTOR_GUIDELINES.md

Product: FLW Mobile App | Org: Piramal Swasthya | Mentor: @drtechie | Complexity: Low

[drtechie]

@Jayant-kernel, please raise PRs.

[Jayant-kernel]

@drtechie i have raised the pr