P6 Stream V: ImageCompression (expect/actual) + CameraPicker polish

Android: BitmapFactory + ExifInterface + JPEG quality 0.7 + 1920px downscale.
iOS: UIImage.jpegData. JVM/JS/WASM: no-op. CameraPicker uses TakePicture
ActivityResult + permission rationale.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

composeApp/src/commonMain/kotlin/com/tt/honeyDue/ui/components/CameraPicker.kt

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+package com.tt.honeyDue.ui.components
+
+/**
+ * Shared camera-picker helpers (commonMain).
+ *
+ * The actual `rememberCameraPicker` composable lives at
+ * `com.tt.honeyDue.platform.rememberCameraPicker` (expect/actual per
+ * platform). This file captures the pure logic that decides *what* to do
+ * when a user taps "Take photo" so it can be unit-tested without touching
+ * the ActivityResult contract or iOS `UIImagePickerController`.
+ *
+ * Mirrors the iOS reference `CameraPickerView.swift`, which simply falls
+ * back to the photo library if the camera source type is unavailable. On
+ * Android we add a permission-rationale step to match Google's UX
+ * guidelines, then delegate to the platform picker.
+ */
+
+/** The three possible outcomes of "user tapped Take photo". */
+enum class CameraPermissionDecision {
+    /** Camera permission already granted — launch the picker immediately. */
+    Launch,
+
+    /** Permission denied previously; show a rationale dialog before asking again. */
+    ShowRationale,
+
+    /** First request (or "don't ask again" cleared) — prompt the OS directly. */
+    Request,
+}
+
+/**
+ * Pure decision function: given the current permission state, return the
+ * next UI action.
+ *
+ * @param isGranted `true` if the camera permission is currently held.
+ * @param shouldShowRationale Android's `shouldShowRequestPermissionRationale`
+ *   flag — `true` when the user has previously denied the permission but
+ *   hasn't selected "don't ask again".
+ */
+fun decideCameraPermissionFlow(
+    isGranted: Boolean,
+    shouldShowRationale: Boolean,
+): CameraPermissionDecision = when {
+    isGranted -> CameraPermissionDecision.Launch
+    shouldShowRationale -> CameraPermissionDecision.ShowRationale
+    else -> CameraPermissionDecision.Request
+}

composeApp/src/commonMain/kotlin/com/tt/honeyDue/util/ImageCompression.kt

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+package com.tt.honeyDue.util
+
+/**
+ * Cross-platform image compression matching the iOS helper
+ * `iosApp/iosApp/Helpers/ImageCompression.swift`.
+ *
+ * Contract:
+ * - Input is a raw encoded-image [ByteArray] (JPEG, PNG, HEIC…).
+ * - Output is a JPEG-encoded [ByteArray] at [quality] (default 0.7), with
+ *   the long edge clamped to [maxEdgePx] (default 1920px) while preserving
+ *   aspect ratio.
+ * - EXIF orientation is applied into the pixel data; the output image is
+ *   always in the canonical "upright" orientation (no orientation tag, or
+ *   `ORIENTATION_NORMAL`).
+ *
+ * Platforms:
+ * - Android → `BitmapFactory` + `ExifInterface` + `Matrix` + JPEG compress.
+ * - iOS → `UIImage(data:)` + `UIImage.jpegData(compressionQuality:)`.
+ *   `UIImage` normalizes EXIF automatically during decode.
+ * - JVM / JS / WASM → no-op pass-through (web/desktop do not run this path
+ *   in production; returning the input keeps common code simple).
+ *
+ * This replaces the size-capped `ImageCompressor` helper for new call sites
+ * that want to match iOS (quality-based, not size-based) semantics.
+ */
+expect object ImageCompression {
+    /**
+     * Compress [input] to JPEG, optionally downscaling.
+     *
+     * @param input encoded image bytes (JPEG/PNG/HEIC supported by the platform).
+     * @param maxEdgePx maximum long-edge size in pixels (aspect preserved).
+     *                  Defaults to `1920` to match iOS.
+     * @param quality JPEG quality in `[0.0f, 1.0f]`. Defaults to `0.7f` to match iOS.
+     * @return compressed JPEG bytes, or the original input on decode failure.
+     */
+    suspend fun compress(
+        input: ByteArray,
+        maxEdgePx: Int = 1920,
+        quality: Float = 0.7f
+    ): ByteArray
+}