docs: retire the last planning file, fold its constraints into PROJECT.md

REQUIREMENTS.md was the same pre-tracker genre as the roadmap and state
snapshot, and had drifted into being wrong rather than merely stale: it
listed the home-screen widget and full-text search under "Out of Scope
(V3+)" when both have shipped.

Its one still-useful part was the Constraints list, so that moves into
PROJECT.md as a section of its own — platform, offline-first, privacy, i18n,
tests/CI, reproducible builds, licence. The tech-stack pins it carried were
already duplicated in PROJECT.md's Stack, which is also where the drift came
from: two files restating the same versions, only one getting updated.

While there: AGP was recorded as 9.1.1, actually 9.2.1, and the Stack
section described no submodule despite floret-kit being a
compiled-from-source composite build.

.planning/ is now just PROJECT.md, which describes the project rather than
its plan.

.planning/PROJECT.md

@@ -28,10 +28,26 @@ Kotlin 2.3.21 (paired with KSP 2.3.9 — Kotlin 2.4.0 has no KSP release
 yet, do not upgrade until one ships). Jetpack Compose + Material 3
 Expressive 1.5.0-alpha21 (alpha is intentional — Expressive APIs only
 live in the 1.5 alpha line). Hilt 2.59.2, DataStore. Gradle Kotlin DSL
-with Version Catalog. AGP 9.1.1, Gradle 9.5.1. JVM target 17.
+with Version Catalog. AGP 9.2.1, Gradle 9.5.1. JVM target 17 (exactly — AGP
+requires it).
 
-Android-only (minSdk 29, targetSdk 36). No iOS. No `INTERNET` permission —
-any feature that would need one is an explicit product decision first.
+The shared Material 3 Expressive kit, **floret-kit**, is a git submodule wired
+in as a Gradle composite build, so it compiles from source rather than resolving
+as a dependency.
+
+## Constraints
+
+- **Platform:** Android-only, Android 10+ (minSdk 29), targetSdk 36. No iOS.
+- **Offline-first:** all data lives in `CalendarContract` — no app database, no
+  sync stack. No `INTERNET` permission; any feature needing one is an explicit
+  product decision first.
+- **Privacy:** zero telemetry, zero analytics.
+- **i18n:** German + English from day one; further languages come from community
+  translators via the self-hosted Weblate, which owns every `values-*` file.
+- **Tests + CI from day one**, JVM-first.
+- **Reproducible release builds**, so the official F-Droid repo can verify the
+  published binary against a from-source rebuild.
+- **Licence:** MIT.
 
 ## Naming
 

.planning/REQUIREMENTS.md

@@ -1,52 +0,0 @@
-# Calendula — Requirements
-
-Architecture reference: [`../docs/ARCHITECTURE.md`](../docs/ARCHITECTURE.md)
-
-## V1 Scope (Variant "B") — shipped in full (v1.0.0, 2026-06-11)
-
-- [x] Foundation & CI infrastructure — v0.1.0 (2026-06-08)
-- [x] Data Layer over `CalendarContract`
-- [x] Permission flow (`READ_CALENDAR`)
-- [x] Month view (S1)
-- [x] Week view (S2)
-- [x] Day view (S3)
-- [x] Event Detail Sheet (S4) — became a full screen, plus full event read (v0.6)
-- [x] Multi-Calendar Filter (M3)
-- [x] Today button (M2) — shipped v0.5; Jump-to-Date **cut from scope**
-- [x] View-Switcher (M1)
-- [x] Settings screen (M4)
-- [x] Empty / no-permission / no-calendars states
-- [x] German + English localization
-- [x] Loading/Failure/Success states per screen (architectural pattern)
-
-## V2 Scope — write support, shipped in full (v2.0.0, 2026-06-11)
-
-- [x] Write foundation: `WRITE_CALENDAR`, read-only-calendar detection, delete (v1.1)
-- [x] Create event: form, FAB, last-used calendar (v1.2; polish v1.2.1)
-- [x] Edit event: shared form, scoped recurring writes, recurrence picker (v1.3)
-- [x] Reminder notifications (v1.4) — **reversal of the original
-  "system handles reminders" assumption:** Calendula targets
-  sole-calendar-app users, so it posts reminder notifications itself
-  (Etar model), incl. `POST_NOTIFICATIONS` onboarding
-- [x] Conflict dialog on save + store polish (v2.0)
-- Quick-add — **cut from scope** (the prefilled form covers it)
-- Calendar switching while editing — moved to v3 backlog
-
-### Out of Scope (V3+)
-
-- Home-screen widget
-- Full-text search
-- Tablet/foldable-specific layouts
-- Locations & People ideas (contact picker, OSM autocomplete) — undecided
-- iOS support (Android-only by design)
-
-## Constraints
-
-- **Tech stack:** Kotlin + Jetpack Compose + Material 3 Expressive, Hilt, DataStore
-- **Tech stack pin:** Hilt 2.59.2 + KSP 2.3.9; Kotlin 2.3.21 (KSP for Kotlin 2.4.0 not released yet). Material 3 pinned to `1.5.0-alpha21` (Expressive APIs only exist in alpha). Re-evaluate when KSP/Material3 stable land.
-- **Platform:** Android 10+ (API 29 minimum), Android 16 (API 36) target
-- **Offline-first:** all data lives in `CalendarContract`; no app-side network
-- **Privacy:** zero telemetry, no analytics
-- **i18n:** German + English from day one
-- **Tests + CI from day one**
-- **License:** MIT