Add Enhanced keyboard feature set

[astroboii47]

What Changed

This ports the main Pastiera Enhanced feature set onto the current upstream Pastiera base. The branch intentionally keeps upstream branding, versioning, and release files unchanged so the diff stays focused on app functionality.

Added

• GIF, sticker, and local media support inside the emoji/media picker.
• Media sending through rich content APIs with a file-sharing fallback for apps that do not accept direct GIF/sticker content.
• A Klipy API key setting under Smart Features instead of shipping a default key.
• Snippets, with searchable shortcut popups for inserting saved emails, usernames, phrases, and other reusable text.
• Emoji and symbol shortcode popups while typing, including completion by selecting from the popup or finishing a shortcode.
• Local next-word prediction support with bundled common phrase fallback data.
• Unified prediction mode, which can show predictions in the existing candidate/variation bar instead of stacking another row.
• Long-press removal for unwanted prediction suggestions.
• Updated emoji assets and emoji search data, including newer emoji entries.
• Optional custom emoji font rendering for the emoji picker and variation/candidate UI.
• Per-app keyboard theme overrides with searchable app selection and overridden apps pinned first.
• Theme management improvements, including clone, rename, delete, key tap/accent color handling, translucency controls, and modifier strip thickness.

Improved

• Prediction insertion now replaces the current word when appropriate and advances suggestions after accepting a predicted word.
• Shortcode and snippet popups follow keyboard theming more closely and fit better in unified mode.
• Emoji/media UI keeps the shared tab bar and close controls consistent while allowing direct access to media.
• SYM/status controls have improved page cycling and selector behavior.
• Candidate, variation, and status bar colors better follow the selected keyboard theme.

Notes

• This is a broad draft PR because it represents the full Enhanced feature set. If preferred, it can be reviewed as a reference branch and split into smaller PRs for merge.
• Fork-only release metadata, Pastiera Enhanced version bumps, and fork changelog entries are intentionally not included here.

Testing

• Built successfully with ./gradlew :app:assembleDebug.

[astroboii47]

Reopening this as the cleaned PR for review. It uses the neutral branch and split commits, so this should be the single place to track the combined Enhanced feature set from here.