feat(ics): import UI — open/receive .ics, 1-vs-many routing

Completes v2.7 Branch 2. Wires the import core into the app:

- Manifest ACTION_VIEW/SEND for text/calendar; MainActivity parses the
  incoming Uri (content/file only, so calendula:// deep-links don't match)
  and routes it through RootScreen → CalendarHost like the other one-shot
  intents.
- ImportViewModel reads + parses the file and routes by count: one event →
  the prefilled create form for review (EventEditViewModel.openImported,
  which freezes the reminder default so the file's reminders win); many →
  ImportScreen with a writable-calendar picker, then a bulk import (UID
  dedup) and a result summary.
- ImportScreen also surfaces parser warnings (skipped recurrence overrides,
  ignored attendees, unknown-timezone fallback). Strings EN+DE.

Package is ui.imports (not ui.import — Java keyword). lint + test +
assembleDebug green. No v2.7 tag until on-device review.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/src/main/AndroidManifest.xml

@@ -47,6 +47,21 @@
                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
 
+            <!-- Open a .ics file (file manager / email attachment / browser). -->
+            <intent-filter>
+                <action android:name="android.intent.action.VIEW" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <category android:name="android.intent.category.BROWSABLE" />
+                <data android:scheme="content" android:mimeType="text/calendar" />
+                <data android:scheme="file" android:mimeType="text/calendar" />
+            </intent-filter>
+            <!-- Receive a .ics shared from another app. -->
+            <intent-filter>
+                <action android:name="android.intent.action.SEND" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <data android:mimeType="text/calendar" />
+            </intent-filter>
+
             <!-- Launcher long-press shortcuts (e.g. "New event"). -->
             <meta-data
                 android:name="android.app.shortcuts"