fix(tooling): build.yml and the deploy workflows pass --flavor to a project with no product flavors

[koniz-dev]

Context

build.yml takes a flavor input (development/staging/production,
default development) and passes it to flutter build. But
android/app/build.gradle.kts defines no product flavors, so:

FAILURE: Build failed with an exception.
* What went wrong:
Task 'assembleDevelopmentRelease' not found in root project 'android' and its subprojects.

[!] Gradle project does not define a task suitable for the requested build.
    The android/app/build.gradle.kts file does not define any custom product
    flavors. You cannot use the --flavor option.

Evidence: run 32966668310
(platform=android, flavor=development).

The web build in the same workflow succeeded, so this was masked - only the
Android and iOS paths consume --flavor.

Discovered while safety-checking an unrelated Gradle edit for #30. Not caused by
that change: Gradle configured successfully and then could not find the task.

Scope

Check every --flavor consumer:

• build.yml (Build Android, Build iOS)
• deploy-android.yml, deploy-ios.yml - these also declare a flavor and have
  never got past Setup Flutter until fix(tooling): flutter-version: 'stable' breaks Setup Flutter in 5 more workflows #24, so their flavor handling has never
  been exercised either.

Two honest options

1. Define the flavors. Add flavorDimensions and
   productFlavors { development / staging / production } to
   android/app/build.gradle.kts, plus the iOS scheme equivalents. Makes the
   workflow inputs real. More surface for a starter to carry, and iOS schemes
   cannot be created from a script here.
2. Drop the flavor inputs. Remove --flavor from the workflows and use the
   existing --dart-define / .env layering, which is what
   docs/guides/configuration.md already describes as the configuration
   mechanism. Simpler, and matches how the project actually configures itself.

Option 2 looks right: the repo's documented configuration story is env layering
plus dart-defines, not Gradle flavors. But this changes a documented workflow
input, so it wants a decision.

Acceptance criteria

1. grep -rn '\-\-flavor' .github/workflows/ is consistent with reality: either
   every referenced flavor exists as a product flavor, or --flavor is gone.
2. A workflow_dispatch run of build.yml with platform=android succeeds
   and uploads an APK artifact. Record the run id.
3. A workflow_dispatch run of build.yml with platform=web still succeeds
   (it does today - do not regress it).
4. If the flavor input is removed, build.yml's input list and any doc that
   mentions choosing a flavor are updated together.
5. deploy-android.yml and deploy-ios.yml are made consistent with whichever
   option is chosen, even though they cannot be dispatched here (they publish).
   State that they were not run.
6. ./scripts/dev/audit_template.sh exits 0.

[koniz-dev]

PASS

Fix in #37; evidence in #38. Evidence: docs/verification/issue-34/.

Decision taken (the issue offered two options): dropped --flavor rather than
declaring product flavors. The web job in the same workflow already omitted
--flavor and passed only --dart-define=ENVIRONMENT - which is why web was the
one platform that built. That working path settled it: app_config.dart:33 reads
ENVIRONMENT from .env or a dart-define, and docs/guides/configuration.md
documents env layering. Gradle flavors were never part of this project's design.
Declaring them would also need iOS schemes, which cannot be created from a script
here.

#	Criterion	Result	Evidence
1	--flavor gone, or every flavor exists	PASS	criteria-1-4-flavor-removed.txt - (no matches); the only remaining mention is the comment recording why
2	platform=android succeeds and uploads an APK	PASS	criteria-2-3-dispatched.txt - run 32971439671 success in 6m23s, android-apks-development 32,223,960 bytes
3	platform=web still succeeds	PASS	same file - run 32971452663 success, web-build-development 14,226,706 bytes
4	Input list and docs updated together	PASS	criteria-1-4-flavor-removed.txt - input renamed flavor -> environment, described as the dart-define it sets
5	Deploy workflows consistent; state they were not run	PASS	criterion-5-deploys.txt
6	./scripts/dev/audit_template.sh exits 0	PASS	audit_template.log

First Android APK this repository has produced

Before: Task 'assembleDevelopmentRelease' not found. After: a 32MB signed-debug
APK artifact. Combined with #24 (which fixed Setup Flutter), the Android build
path works end to end for the first time.

On the input rename

flavor -> environment. Calling it a flavor is what made the mistake plausible:
it read like a Gradle product flavor, so someone passed it as one. The input now
says exactly what it does - the value handed to --dart-define=ENVIRONMENT.

A wrong assumption, caught

I asserted deploy-ios.yml also carried a commented --flavor line and wrote an
edit with an assertion to prove it. The assertion failed - that file never had
one. Only deploy-android.yml did. Recorded in the evidence rather than quietly
corrected.