Blossom security analysis fixes

[KoalaSat]

What does this PR do?

Fixes #2536

coordinator opt-in for Blossom image uploads in chat

Coordinators can now choose whether to offer encrypted image uploads (Blossom) in the trade chat by setting an environment variable. If a coordinator does not offer it, the upload button is greyed out with a tooltip explaining why.

Android stack overflow

Replaced String.fromCharCode.apply(null, Array.from(data)) with a chunked loop (8192-byte chunks), matching the already-safe getBinary pattern

EXIF metadata leak

Added stripImageMetadata() — canvas re-encode before encryption strips all EXIF/GPS/camera data. WebP/GIF animations are flattened to a single frame. Falls back to original file if canvas is unavailable

SVG tracking risk nip17File.ts

Changed isImageMimeType from startsWith('image/') to an explicit allowlist ['image/jpeg', 'image/png', 'image/webp', 'image/gif'] — SVG excluded originalSha256 unverified MessageCard/index.tsx Added verifyBlobHash(plaintext, fileData.originalSha256) after decryption as defence-in-depth

nodeapp missing /blossom/ route

nodeapp/coordinators/{temple,lake,bazaar,freedomsats,alice}/locations.conf Added location /mainnet|testnet/{alias}/blossom/ with proxy_pass, proxy_http_version 1.1, Host $host, and client_max_body_size 12m to all 5 coordinators (10 location blocks total)

Checklist before merging

• Install pre-commit and initialize it: pip install pre-commit, then pre-commit install. Pre-commit installs git hooks that automatically check the codebase. If pre-commit fails when you commit your changes, please fix the problems it points out.