feat: rich character profiles — brand voice, target, rules, hashtag profiles

Backend:
- Character model: add brand_voice, target_audience, business_goals,
  products_services, content_rules (JSON do/dont), hashtag_profiles (JSON)
- Content generation: inject full character context into LLM system prompt
  (voice, audience, goals, products, rules)
- Hashtag generation: merge always-on tags from profile with AI-generated tags
- Schema: update CharacterBase and CharacterUpdate with new fields

Frontend:
- CharacterForm: new sections "Identità e Voce", "Regole Contenuti",
  "Profili Hashtag" with dedicated editors
- RulesEditor: do/don't list with add/remove
- HashtagProfileEditor: per-platform tabs, fixed hashtags + max generated count
- All fields loaded on edit, saved on submit

DB migration: 6 new columns added to characters table

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/services/content.py

@@ -20,7 +20,9 @@ def generate_post_text(
     """Generate social media post text based on a character profile.
 
     Args:
-        character: Dict with keys: name, niche, topics (list), tone (str).
+        character: Dict with keys: name, niche, topics (list), tone (str),
+                   and optional rich profile: brand_voice, target_audience,
+                   business_goals, products_services, content_rules.
         topic_hint: Optional topic suggestion to guide generation.
         llm_provider: LLM provider instance for text generation.
         platform: Target platform (e.g. 'instagram', 'facebook', 'tiktok', 'youtube').
@@ -36,18 +38,56 @@ def generate_post_text(
 
     topics_str = ", ".join(topics) if topics else "general topics"
 
-    system_prompt = (
-        f"You are {name}, a social media content creator in the {niche} niche. "
-        f"Your expertise covers: {topics_str}. "
-        f"Your communication style is {tone}. "
-        f"You create authentic, engaging content that resonates with your audience. "
-        f"Never reveal you are an AI. Write as {name} would naturally write.\n\n"
-        f"REGOLA CRITICA: Se ti viene indicata una tecnica narrativa (PAS, AIDA, Storytelling, ecc.), "
-        f"usala SOLO come struttura invisibile del testo. "
-        f"NON scrivere MAI le etichette del framework nel post (es. non scrivere 'PROBLEMA:', "
-        f"'AGITAZIONE:', 'SOLUZIONE:', 'ATTENZIONE:', 'INTERESSE:', ecc.). "
-        f"Il lettore non deve percepire alcun framework — deve sembrare un post naturale e spontaneo."
-    )
+    # Base identity
+    system_parts = [
+        f"You are {name}, a social media content creator in the {niche} niche.",
+        f"Your expertise covers: {topics_str}.",
+        f"Your communication style is {tone}.",
+    ]
+
+    # Rich profile: brand voice
+    brand_voice = character.get("brand_voice")
+    if brand_voice:
+        system_parts.append(f"\nVOCE E STILE DI COMUNICAZIONE:\n{brand_voice}")
+
+    # Rich profile: target audience
+    target_audience = character.get("target_audience")
+    if target_audience:
+        system_parts.append(f"\nPUBBLICO TARGET:\n{target_audience}")
+
+    # Rich profile: business goals
+    business_goals = character.get("business_goals")
+    if business_goals:
+        system_parts.append(f"\nOBIETTIVI BUSINESS:\n{business_goals}")
+
+    # Rich profile: products/services
+    products_services = character.get("products_services")
+    if products_services:
+        system_parts.append(f"\nPRODOTTI/SERVIZI OFFERTI:\n{products_services}")
+
+    # Rich profile: content rules (do/don't)
+    content_rules = character.get("content_rules") or {}
+    do_rules = content_rules.get("do", [])
+    dont_rules = content_rules.get("dont", [])
+    if do_rules or dont_rules:
+        rules_text = "\nREGOLE CONTENUTI:"
+        if do_rules:
+            rules_text += "\nFA SEMPRE: " + " | ".join(do_rules)
+        if dont_rules:
+            rules_text += "\nNON FARE MAI: " + " | ".join(dont_rules)
+        system_parts.append(rules_text)
+
+    system_parts.extend([
+        "\nYou create authentic, engaging content that resonates with your audience.",
+        "Never reveal you are an AI. Write as {name} would naturally write.",
+        "\nREGOLA CRITICA: Se ti viene indicata una tecnica narrativa (PAS, AIDA, Storytelling, ecc.), "
+        "usala SOLO come struttura invisibile del testo. "
+        "NON scrivere MAI le etichette del framework nel post (es. non scrivere 'PROBLEMA:', "
+        "'AGITAZIONE:', 'SOLUZIONE:', 'ATTENZIONE:', 'INTERESSE:', ecc.). "
+        "Il lettore non deve percepire alcun framework — deve sembrare un post naturale e spontaneo.",
+    ])
+
+    system_prompt = "\n".join(system_parts)
 
     # Platform-specific instructions
     platform_guidance = {