Make Formulus settings QR codes camera-scannable via formulus:// deep link

[r0ssing]

Summary

Update the Formulus settings QR payload so it can be scanned by the system camera (Android first; investigate iOS) and open Formulus into the settings / profile flow, instead of only working when scanned from the in-app Settings scanner.

Today the QR encodes an opaque FRMLS:… string (FRMLSHelpers, Portal, synk qr, formulus/scripts/generateQR.ts). That is not a URI, so OS cameras do not offer an “Open in Formulus” action.

Proposed URI shape

Prefer a custom URL scheme (not an https://opendataensemble.org/… App/Universal Link):

formulus://settings?<FRMLS payload>

Rationale: best fit for app-only deep links. Catching a shared opendataensemble.org HTTPS path risks colliding with normal website / docs QR codes.

Exact query encoding can be finalized in implementation (e.g. wrap the existing FRMLS string in a query param). Keep the FRMLS body as the credential payload.

Requirements

Formulus (consume path)

• Register an Android intent filter for the formulus:// scheme (path/host for settings as needed).
• On cold/warm start from such a URI: navigate into the settings/profile flow and treat the payload like an in-app QR scan.
• Confirmation before applying: show a confirmation dialog before saving. Likely lands after Formulus profiles work lands — in practice this becomes “Add new profile” + confirm before persist (same effective outcome as scanning in-app, with an explicit confirm step).
• Backward compatibility: in-app scanner must continue to accept bare FRMLS:… codes (no URI wrapper).
• Deep-linked URIs that contain FRMLS must parse the same fields (serverUrl / username / password) via existing QRSettingsService / decodeFRMLS path (or a thin wrapper around it).

iOS

• Spike whether the same formulus://settings?… custom scheme is feasible (URL types in Info.plist + Linking), and whether OS Camera / Control Center scanner surfaces an open-app affordance comparable to Android.
• If iOS system-camera open is weak or unreliable, ship Android first and document iOS as follow-up or in-app-only for now.

Generators (same issue)

Update all producers to emit the new URI-wrapped form (while documenting that bare FRMLS remains readable in-app):

• Synkronus Portal (synkronus-portal FRMLS / formulus QR helpers)
• Synkronus CLI (synk qr)
• Formulus script formulus/scripts/generateQR.ts

Acceptance criteria

• Android: scanning a new-format settings QR with the system camera can open Formulus and reach the settings/profile apply flow with confirmation before save.
• In-app Settings scanner still accepts bare FRMLS:… and the new formulus://settings?… form.
• Portal, synk qr, and generateQR.ts emit the new URI format.
• Short note in the PR/issue on iOS feasibility and whether iOS is in-scope for the same change or deferred.
• No hijacking of general opendataensemble.org HTTPS links for this feature.

Notes / context

• Current encode format: FRMLS:v:<b64>;s:<b64>;u:<b64>;p:<b64>;;
• Related code: formulus/src/utils/FRMLSHelpers.ts, formulus/src/services/QRSettingsService.ts, formulus/src/screens/SettingsScreen.tsx, Portal frmls / formulus QR utils, synkronus-cli qr command.
• Profiles dependency: confirmation / “Add new profile” behavior may intentionally follow the profiles work.