Add CLAUDE.md with topic-specific context docs

Split project context into .claude/context/ (architecture, server,
styling, standards) instead of one large file, referenced from a
minimal root CLAUDE.md.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.claude/context/standards.md

@@ -0,0 +1,55 @@
+# Code standards
+
+## Linting
+
+`analysis_options.yaml` includes `package:flutter_lints/flutter.yaml` with
+no rules added/relaxed. Run `flutter analyze` before considering a change
+done; it should stay clean.
+
+## Comments
+
+Comments are used sparingly and only for non-obvious *why* — a hidden
+constraint, a workaround, or the rationale for overriding a framework
+default. See `AppTheme._pageTransitionsTheme`/`_sliderTheme`,
+`NextcloudService._parseDavDate`/`_davPath`, and `LoginFlowService`'s class
+doc comment for the house style: one short doc comment on the
+class/function explaining *why* it exists, not what each line does. Don't
+add comments that restate the code or describe what a well-named
+class/method already makes obvious.
+
+## Widget structure
+
+- Screens (`views/`) are typically `StatefulWidget` when they own
+  controllers/local UI state (e.g. `LoginView`'s form key + text
+  controller); presentation is frequently split into small private
+  `StatelessWidget`s in the same file (`_ServerForm`, `_WaitingForBrowser`
+  in `login_view.dart`) rather than inlined in one large `build`. Follow
+  this split for any view complex enough to have more than one visual
+  "mode".
+- Private helpers/widgets are prefixed with `_` and live in the same file as
+  their one caller; promote to `widgets/` only once something is reused
+  across files.
+- Read provider state with `context.watch<ServerProvider>()` in `build`,
+  and `context.read<ServerProvider>()` for one-off calls from callbacks
+  (matches `LoginView._handleContinue`).
+
+## Testing
+
+- Widget tests must mock platform channels that the app touches on startup
+  — `SharedPreferences.setMockInitialValues({})` and a mock
+  `MethodChannel('plugins.it_nomads.com/flutter_secure_storage')` handler —
+  and disable Google Fonts network fetching
+  (`GoogleFonts.config.allowRuntimeFetching = false`) in `setUpAll`. Without
+  these, `ServerProvider`'s session restore never resolves in the test
+  sandbox (no plugin implementation is registered, so the read future just
+  never completes) and the app stays on `_SplashView`'s indeterminate
+  spinner, which makes `pumpAndSettle()` hang until its own timeout instead
+  of failing fast. See `test/widget_test.dart` for the reference setup.
+- Run with `flutter test`.
+
+## Dependencies
+
+Networking is deliberately split: `package:http` for simple JSON/XML
+request-response calls, `package:dio` only where streaming/progress is
+needed (downloads). Don't introduce a third HTTP client — extend the
+existing split instead.