feat: add FastAPI backend with PostgreSQL and start script fixes

- Add server/ directory with FastAPI backend
- Fix server/start.sh to properly handle venv on Windows/Git Bash
- Add alembic migrations and pyproject.toml
- Add server tests

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

server/src/app/schemas/bootstrap.py

@@ -0,0 +1,67 @@
+from __future__ import annotations
+
+from pydantic import BaseModel, EmailStr, Field, field_validator
+
+
+class BootstrapCompanyRead(BaseModel):
+    name: str
+    code: str
+    admin_email: str
+
+
+class BootstrapConnectionRead(BaseModel):
+    host: str
+    port: int
+
+
+class BootstrapDatabaseRead(BaseModel):
+    driver: str
+    host: str
+    port: int
+    name: str
+    username: str
+    password_configured: bool
+
+
+class BootstrapCacheRead(BaseModel):
+    enabled: bool
+    url: str
+
+
+class BootstrapStateRead(BaseModel):
+    initialized: bool
+    company: BootstrapCompanyRead
+    web: BootstrapConnectionRead
+    server: BootstrapConnectionRead
+    database: BootstrapDatabaseRead
+    redis: BootstrapCacheRead
+
+
+class BootstrapSetupPayload(BaseModel):
+    company_name: str = Field(min_length=2, max_length=80)
+    company_code: str = Field(default="", max_length=32)
+    admin_email: EmailStr | None = None
+
+    postgres_host: str = Field(min_length=1, max_length=255)
+    postgres_port: int = Field(default=5432, ge=1, le=65535)
+    postgres_db: str = Field(min_length=1, max_length=128)
+    postgres_user: str = Field(min_length=1, max_length=128)
+    postgres_password: str = Field(min_length=1, max_length=255)
+
+    redis_url: str | None = Field(default=None, max_length=255)
+
+    @field_validator(
+        "company_name",
+        "company_code",
+        "postgres_host",
+        "postgres_db",
+        "postgres_user",
+        "postgres_password",
+        "redis_url",
+        mode="before",
+    )
+    @classmethod
+    def strip_string(cls, value: str | None) -> str | None:
+        if value is None:
+            return None
+        return value.strip()