Fix translated chat text links losing URL entities

[Rocket-Space]

Motivation

• Translating whole messages could modify or move visible link text and cause text_link/URL entities to be lost because the original token-based masking did not survive reordering by the translator.
• The change aims to preserve link identity and original URLs even when the translator alters the visible text or its position.

Description

• Updated TranslationHelper.maskLinks to emit tagged placeholders that include an ID and the original visible text using the format [[ENT_START_n]]...[[ENT_END_n]] instead of a plain token. (TMessagesProj/src/main/java/org/spacegram/translator/TranslationHelper.java).
• Added an id field to LinkPlaceholder and store original url and textUrl flags to map translated fragments back to their original entities. (LinkPlaceholder).
• Implemented restoreTaggedEntities(...) which parses the [[ENT_START_n]]...[[ENT_END_n]] blocks from translated output, inserts the translated visible text into the result, and reconstructs TL_messageEntityTextUrl / TL_messageEntityUrl entities with correct offsets and original URLs. (restoreTaggedEntities + fallback to legacy restoration).
• Kept a backward-compatible fallback that still handles the legacy token-style placeholders if the translation provider does not return the new tags.

Testing

• Attempted to compile the module with ./gradlew :TMessagesProj:compileDebugJavaWithJavac -x lint, but the build failed due to the local Java/Gradle environment mismatch (Unsupported class file major version 69), so no successful compilation artifacts were produced on the runner.

---

Codex Task