Train timetable, keyless map, NBS rates, and weekly content sync

[ialakey]

Works through the remaining items in the backlog: two new screens, a fifth rate
source, a broader weekly content sync, and content updates that no longer wait
for a Play release. Every external source was verified live before anything was
built on it.

Recolour

The seed colour was the Serbian flag red, and Material 3 tints every surface
with the seed — which is why backgrounds and cards came out pink rather than
just the accents. The palette is now a blue accent over a neutral surface
ramp: colour marks actions, the active tab and an urgent deadline, and
nothing else. Cards gained a hairline border since they are no longer separated
from the background by tint.

Train timetable

Serbian Railways' site is a jQuery front end over a JSON station lookup and two
server-rendered result pages. The app uses the same endpoints:

• Route — direct services between two stations on a date.
• Board — departures or arrivals for one station.

Stations you have used are remembered, so the usual trip takes two taps. Each
result is rendered twice by the operator (wide and narrow layouts), so the row
layouts are pinned down in one service rather than spread through the UI.

Verified live: 36 connections and 98 board entries parsed for Beograd Centar.

Map without an API key

362 relocant-run businesses from the stats.srb.guide catalogue on an
OpenStreetMap map. OSM needs no API key and no billing account, which is
what made this practical — the Google Maps SDK needs both.

The catalogue is bundled, so the list, the search and the category filters work
offline; only the tiles need a connection. Categories get their own icon and
colour, and each place links out to Google Maps for directions.

Its API requires auth, so the catalogue is read from the map page's hydration
payload, which robots.txt allows. Records are located by id and each field is
then read from that record's own window — field order varies between records,
and a single fixed-order pattern silently dropped 28 of them.

Exchange rates: a fifth source

Adds the National Bank of Serbia official rate. It is the only source with a
real API, and it replaces the previous reference rate, which was scraped out of
one office's ticker as a side effect.

Reference sources are now flagged and excluded from the "best rate"
comparison — the NBS is not a counter you can walk up to. RUB and GBP have no
NBS cash rate, so those fall back to the non-cash figure.

All five verified live in test/exchange_parsers_live_test.dart.

Content sync covers three datasets

sync-guide.yml becomes sync-content.yml and now refreshes weekly:

Dataset	Source	Records
guide.json	srb.guide	74 articles
places.json	stats.srb.guide/map	362 places (new)
tg_chats.json	stats.srb.guide	432 chats (was 340)

The chat directory had drifted — it was a hand-maintained list of 340 entries.
It now comes from the catalogue with topic, size and whether each chat is still
active, while keeping the original name/url/group keys so the existing
screen keeps working.

Only datasets whose payload actually changed are staged, so a new sync
timestamp alone never produces a commit.

Guide updates between releases

Because that workflow commits the guide to master, the app now checks GitHub
for a newer copy once a day, conditional on an ETag so an unchanged guide
costs a single 304 and no body transfer. A correction on srb.guide reaches
users in days instead of waiting for a Play release.

The download is validated before it is accepted — the same shape checks CI runs
— and the bundled asset stays the fallback, so a bad fetch can never leave the
app without content. Settings gains a manual check.

Search

Article text was re-lowercased on every keystroke: 1.5 MB per search, with
the search debounced to every 200 ms. The lowercased forms are now computed once
per article and reused.

One item I did not implement

The backlog asked for SQLite + FTS5. I measured before building it, and the
numbers argue against it at this size:

• Search over all 74 articles currently takes ~12 ms.
• The APK cost of guide.json is already ~0.5 MB, not 2.4 MB — Android
  compresses assets, and the file gzips to 0.53 MB.
• SQLite would not shrink that. A prebuilt .db is about the same size, and
  building the index on device means shipping the JSON and storing the DB, so
  on-device usage goes up.
• package:sqlite3 3.x compiles SQLite from source through Dart build hooks,
  which is a new native dependency in the Android and CI build I would rather
  not add for a 12 ms operation.

So the cost is a native dependency and build risk, and the benefit is nil until
the content is several times larger. I did the part that was actually costing
something — the per-keystroke lowercasing above. Happy to add FTS5 if you want
it regardless; the search API is already isolated behind GuideRepository.

Housekeeping

Removed assets/data/media/ — 112 images, 5.6 MB, that nothing referenced.
They were never declared under assets: in pubspec.yaml (a bare
assets/data/ entry does not recurse), so they were not in the APK either; they
only sat in the repository. They predate the guide re-sync: the old guide's
image links were site-relative paths like /guides/business/open/media/…webp,
addresses on srb.guide rather than local files, whose names do not match these.
Checked before deleting — no Dart loads assets/data/media, no bundled dataset
points at assets/, and the app builds and renders articles without it.

Updated the actions to their current majors. GitHub was force-running the
Node 20 ones on Node 24 and warning on every run, and setup-java v4 is
explicitly no longer maintained:

actions/checkout                 v4 -> v7
actions/setup-java               v4 -> v6
actions/upload-artifact          v4 -> v7
actions/github-script            v7 -> v9
peter-evans/create-pull-request  v6 -> v8
softprops/action-gh-release      v2 -> v3

subosito/flutter-action stays on v2, still its current major. Every tag was
checked to exist before pinning, and the inputs used here are unchanged across
these majors.

Verification

• dart format, flutter analyze (0 issues), 29 unit tests, guide validation
• All five rate sources and all three timetable endpoints verified against the
  live sites
• Release AAB builds; merged manifest keeps targetSdk 36 / minSdk 24 and
  gains no new permissions
• Exercised on an Android 16 emulator: new theme in light and dark, the map with
  tiles and 362 markers, a train search returning real departures, and the rates
  screen showing NBS alongside the four offices