feat: Kokoro 82M TTS engine + voice profile type system

Add Kokoro-82M as a new TTS engine — 82M params, CPU realtime, 8 languages,
Apache 2.0. Unlike cloning engines, Kokoro uses pre-built voice styles, which
required a new profile type system to support non-cloning engines cleanly.

Kokoro engine:
- New kokoro_backend.py implementing TTSBackend protocol
- 50 built-in voices across en/es/fr/hi/it/pt/ja/zh
- KPipeline API with language-aware G2P routing via misaki
- PyInstaller bundling for misaki, language_tags, espeakng_loader, en_core_web_sm

Voice profile type system:
- New voice_type column: 'cloned' | 'preset' | 'designed' (future)
- Preset profiles store engine + voice ID instead of audio samples
- default_engine field on profiles — auto-selects engine on profile pick
- Create Voice dialog: toggle between 'Clone from audio' and 'Built-in voice'
- Edit dialog shows preset voice info instead of sample list for preset profiles
- Engine selector locks to preset engine when preset profile is selected
- Profile grid filters by engine — shows Kokoro voices when Kokoro selected
- Custom empty state when no preset profiles exist for selected engine

Bug fixes:
- Fix relative audio paths in DB causing 404s in production builds
- config.set_data_dir() now resolves to absolute paths
- Startup migration converts existing relative paths to absolute

Also updates PROJECT_STATUS.md and tts-engines.mdx developer guide.

backend/database/migrations.py

@@ -34,6 +34,7 @@ def run_migrations(engine) -> None:
     _migrate_generations(engine, inspector, tables)
     _migrate_effect_presets(engine, inspector, tables)
     _migrate_generation_versions(engine, inspector, tables)
+    _resolve_relative_paths(engine, tables)
 
 
 # -- helpers ---------------------------------------------------------------
@@ -134,6 +135,17 @@ def _migrate_profiles(engine, inspector, tables: set[str]) -> None:
         _add_column(engine, "profiles", "avatar_path VARCHAR", "avatar_path")
     if "effects_chain" not in columns:
         _add_column(engine, "profiles", "effects_chain TEXT", "effects_chain")
+    # Voice type system — v0.3.x
+    if "voice_type" not in columns:
+        _add_column(engine, "profiles", "voice_type VARCHAR DEFAULT 'cloned'", "voice_type")
+    if "preset_engine" not in columns:
+        _add_column(engine, "profiles", "preset_engine VARCHAR", "preset_engine")
+    if "preset_voice_id" not in columns:
+        _add_column(engine, "profiles", "preset_voice_id VARCHAR", "preset_voice_id")
+    if "design_prompt" not in columns:
+        _add_column(engine, "profiles", "design_prompt TEXT", "design_prompt")
+    if "default_engine" not in columns:
+        _add_column(engine, "profiles", "default_engine VARCHAR", "default_engine")
 
 
 def _migrate_generations(engine, inspector, tables: set[str]) -> None:
@@ -168,3 +180,47 @@ def _migrate_generation_versions(engine, inspector, tables: set[str]) -> None:
     columns = _get_columns(inspector, "generation_versions")
     if "source_version_id" not in columns:
         _add_column(engine, "generation_versions", "source_version_id VARCHAR", "source_version_id")
+
+
+def _resolve_relative_paths(engine, tables: set[str]) -> None:
+    """Resolve any relative file paths in the database to absolute paths.
+
+    Earlier versions stored paths relative to CWD (e.g. "data/generations/abc.wav").
+    These break when the production binary's CWD differs from the data directory.
+    This migration converts them to absolute paths using the configured data dir.
+    Idempotent: absolute paths are left untouched.
+    """
+    from pathlib import Path
+
+    path_columns = [
+        ("generations", "audio_path"),
+        ("generation_versions", "audio_path"),
+        ("profile_samples", "audio_path"),
+        ("profiles", "avatar_path"),
+    ]
+
+    total_fixed = 0
+    with engine.connect() as conn:
+        for table, column in path_columns:
+            if table not in tables:
+                continue
+            rows = conn.execute(
+                text(f"SELECT id, {column} FROM {table} WHERE {column} IS NOT NULL")
+            ).fetchall()
+            for row_id, path_val in rows:
+                if not path_val:
+                    continue
+                p = Path(path_val)
+                if p.is_absolute():
+                    continue
+                # Resolve relative to CWD (which is where they were created)
+                resolved = p.resolve()
+                if resolved.exists():
+                    conn.execute(
+                        text(f"UPDATE {table} SET {column} = :path WHERE id = :id"),
+                        {"path": str(resolved), "id": row_id},
+                    )
+                    total_fixed += 1
+        if total_fixed > 0:
+            conn.commit()
+            logger.info("Resolved %d relative file paths to absolute", total_fixed)

backend/database/models.py

@@ -10,7 +10,13 @@ Base = declarative_base()
 
 
 class VoiceProfile(Base):
-    """Voice profile."""
+    """Voice profile.
+
+    voice_type discriminates three flavours:
+      - "cloned"   — traditional reference-audio profiles (all cloning engines)
+      - "preset"   — engine-specific pre-built voice (e.g. Kokoro voices)
+      - "designed"  — text-described voice (e.g. Qwen CustomVoice, future)
+    """
 
     __tablename__ = "profiles"
 
@@ -20,6 +26,14 @@ class VoiceProfile(Base):
     language = Column(String, default="en")
     avatar_path = Column(String, nullable=True)
     effects_chain = Column(Text, nullable=True)
+
+    # Voice type system — added v0.3.x
+    voice_type = Column(String, default="cloned")  # "cloned" | "preset" | "designed"
+    preset_engine = Column(String, nullable=True)   # e.g. "kokoro" — only for preset
+    preset_voice_id = Column(String, nullable=True)  # e.g. "am_adam" — only for preset
+    design_prompt = Column(Text, nullable=True)      # text description — only for designed
+    default_engine = Column(String, nullable=True)   # auto-selected engine, locked for preset
+
     created_at = Column(DateTime, default=datetime.utcnow)
     updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)